Most of the time, Leonard (Johnny Galecki) has no lenses in his glasses.

Mayim Bialik is the only cast member to have a PhD. In 2008, she completed her neuroscience studies and earned her PhD in Neuroscience.

Jim Parsons' audition for the role of Dr. Sheldon Cooper was so good that creator Chuck Lorre immediately asked him to come in for a second one, because Lorre wanted to be one hundred percent sure Parsons was as brilliant as he seemed. After the second audition went perfectly, Lorre cast him on the spot.

During the third season, the producers became aware of a series called "The Theorists," produced and broadcast in the country of Belarus, that was a virtual copy of this show. Legal action over copyright infringement would have been futile, since the production company was pretty much owned by the Belarus government. However, a lawsuit turned out not to be necessary, because when word got out that the show was a rip-off, the actors and actresses quit, and the show was immediately cancelled.

When Sheldon (Jim Parsons) plays the theremin (which is widely regarded as one of the hardest instruments to play), that is actually Jim Parsons playing it.

The two main characters (Sheldon Cooper (Jim Parsons) and Leonard Hofstadter (Johnny Galecki)) are named after late television producer Sheldon Leonard.

Sheldon (Jim Parsons) can be seen wearing various versions of "Flash" t-shirts throughout the series. In the series The Flash (2014), character Cisco Ramon (Carlos Valdes) frequently wears "The Big Bang Theory"-based shirts, such as one with Sheldon's catchphrase "Bazinga!"

During a first season episode Raj (Kunal Nayyar), Leonard (Johnny Galecki), and Howard (Simon Helberg) are trying to find a fourth person to replace Sheldon (Jim Parsons) on their physics bowl team. Raj suggests Mayim Bialik, saying, "You know who's apparently very smart, is the girl who played TV's Blossom (1990). She got a PhD. in neuroscience or something." Leonard responds, "Raj, we're not getting TV's Blossom to join our physics bowl team." During season three, Bialik started playing the regular role of Dr. Amy Farrah-Fowler on the show. Dr. Fowler has a PhD. like Dr. Bialik, in Neurobiology, a.k.a. Neuroscience.

Raj (Kunal Nayyar)'s inability to talk to women except when consuming alcohol is based on an old co-worker of Executive Producer Bill Prady, when he worked at a computer company.

In fall 2010 Kaley Cuoco revealed to CBS's Watch! Magazine's Behind the Scenes (2008) that she and her co-star and love interest Johnny Galecki had secretly dated for two years earlier in the run of the show, but they are no longer together.

Penny (Kaley Cuoco) has been using the same purse since season one, episode two.

Kaley Cuoco missed filming two episodes of season four because of a broken leg that was the result of a horseback riding accident. In her first appearance following the accident, she was filmed standing behind a counter.

Despite the fact that some viewers take Sheldon's behavior, mannerisms, and social skills as a sign that he has Asperger's syndrome, or otherwise falls on the autism spectrum, the producers have persistently denied in many interviews that Sheldon has Asperger's or any other type of autism. It should be noted, however, that Jim Parsons (Sheldon) has stated that he does think that Sheldon actually does have Asperger's syndrome, and portrays him as such.

On January 14, 2011, CBS gave the series a rare vote of confidence when it issued a three-year renewal through the 2013-14 season. It then received another three-season renewal on March 12, 2014, meaning the show will run at least twelve seasons. This marked the first time in modern television history a scripted television series received back-to-back three-season renewals.

Even though Jim Parsons' character Sheldon Cooper is a huge Star Trek (1966) fan, Parsons himself has never seen the show. The same is true for Doctor Who (1963).

On January 3, 2013, a team of Brazilian biologists announced their name for a newly-discovered species of orchid bee: Euglossa bazinga. This was to honor the show, and specifically Sheldon (Jim Parsons)'s mocking catchphrase "bazinga". Long mistaken for another bee, Euglossa ignita, the new species was deliberately tagged "bazinga" for its history of fooling entomologists. Executive Producer Steven Molaro responded in a press release: "We are always extremely flattered when the science community embraces our show. Sheldon would be honored to know that Euglossa bazinga was inspired by him. In fact, after Mothra (1961) and griffins, bees are his third-favorite flying creature."

Sheldon (Jim Parsons) frequently wears t-shirts with the characters or symbols of the Green Lantern, the Flash, or the old television show The Greatest American Hero (1981). The shirts from the "Green Lantern" comic book series are various colors with a corresponding symbol, with each color representing a different corps of heroes or villains (Red Lanterns, Orange Lanterns, et cetera). In the comics, each color also represents an emotion, thus possibly giving the viewer a clue to Sheldon's temperament for the day.

Although Sheldon does not drive, Jim Parsons gets motion sickness from riding in cars, and prefers to drive them.

Johnny Galecki was originally approached to play Sheldon, but felt that he would be better fit to play the role of Leonard.

Sheldon (Jim Parsons)'s soothing song, "Soft Kitty", is based on an Australian children's song from Executive Producer Bill Prady's daughter's pre school. The song has been featured on Australian children's television show Play School (1966).

Floors two, three and four of Sheldon (Jim Parsons) and Leonard (Johnny Galecki)'s apartment building are the same set just re-dressed for each scene. This can be seen in the fact that the scuff marks on the molding are identical on each level as they walk up the stairs.

On five episodes or more of season six, Mayim Bialik's right hand was hidden in certain ways and camera shots to conceal the the injury she received, and the glove she wore to cover it, from an automobile accident in August of 2012.

Kevin Sussman, who plays Stuart Bloom the comic book store owner, actually worked in a comic book store before becoming an actor.

Sheldon (Jim Parsons) didn't always have his door-knocking quirk. In season one, episode five, The Big Bang Theory: The Hamburger Postulate (2007), he knocks on Penny (Kaley Cuoco)'s door without knocking and calling her three times.

The full names and occupations of the characters are as follows: Dr. Leonard Leakey Hofstader, Ph.D., Experimental Physicist (played by Johnny Galecki); Dr. Sheldon Lee Cooper, B.S., M.S., M.A., Ph.D., Sc.D., Theoretical Physicist (played by Jim Parsons); Howard Joel Wolowitz, M.Eng, Aerospace Engineer (played by Simon Helberg); Dr. Rajesh Ramayan Koothrappali, Ph.D., Astrophysics (played by Kunal Nayyar); Dr. Bernadette Mary Ann Rostenkowski Wolowitz, Ph.D., Microbiology (played by Melissa Rauch); and Dr. Amy Farrah Fowler, Ph.D., Neurobiology (played by Mayim Bialik). Penny's (Kaley Cuoco) last name was never revealed.

Each of the male characters has a signature clothing article that is worn in virtually every episode: Sheldon (Jim Parsons), t-shirts worn over long-sleeve shirts; Leonard (Johnny Galecki), hoodies worn over a t-shirt and under a jacket; Raj (Kunal Nayyar), sweater-vest worn over a shirt, and usually under some type of outerwear; Howard (Simon Helberg), dickie worn under some type of outerwear. Howard usually has a pin on the left side of his dickie of the head of a space alien, and he wears large belt buckles.

Sara Gilbert (Leslie) who plays a former girlfriend of Leonard's, also played Johnny Galecki's girlfriend in Roseanne (1988). Laurie Metcalf, who plays Sheldon (Jim Parsons)'s mother, was also his co-star in Roseanne (1988) and Sara Gilbert's aunt.

With the exception of the pilot, every show name follows the same format as the show's title, that being the name of a scientific episode or theory.

The theme song uses the line "Autotrophs began to drool." This is a science joke. The word "autotroph" means "self-nourishing" and refers to life-forms (plants and algae) that create their own food internally and don't need to eat.

As the series progressed, each taping of the show was attended by Caltech students.

Jim Parsons (Sheldon) and Kaley Cuoco (Penny) are the world's highest paid television actor and actress, with earnings of twenty-nine million dollars and twenty-eight and a half million dollars, having made that income from June 1, 2014 to June 1, 2015. (Forbes 2015)

It was the decision of Jim Parsons to leave the show at the end of the twelfth season that led to its cancellation at the end of that season.

Both Raj (Kunal Nayyar)'s and Bernadette (Melissa Rauch) and Howard (Simon Helberg)'s apartment are filmed on the same set, and are just completely redecorated to change scene, this is why it is rare to see both apartments in one episode.

During his appearance on Inside the Actors Studio Jim Parsons revealed his three favorite scenes: Sheldon receiving a gift from Penny (Kaley Cuoco) - a napkin signed and used by Leonard Nimoy, Sheldon presenting Amy (Mayim Bialik) the relationship agreement, and Sheldon drinking Long Island Iced Tea for the first time.

Out of the main male cast members, Howard (Simon Helberg) is the only one who hasn't seen Penny (Kaley Cuoco) naked in person, despite being the first to flirt with her.

Laurie Metcalf, who plays Sheldon's mother Mary Cooper, is the mother of Zoe Perry, who plays Sheldon's mother Mary Cooper on "Young Sheldon".

Bernadette did not originally have such a high pitched voice. When she first appeared, she had a rather normal pitch voice and as her character began to take shape, she adopted the quirky high pitched voice which Melissa Rauch says she based off her mother's voice "without the Jersey".

The equations written on the boards in various episodes that Leonard (Johnny Galecki)and Sheldon (Jim Parsons) are working on, are real physics equations and are verified as accurate by consulting physicists.

Sheldon, played by Jim Parsons, is from Texas, as is Jim Parsons.

Kaley Cuoco presented the Best Performance by an Actor in a television series, musical or comedy at the 2011 Golden Globe Awards to her co-star Jim Parsons.

Jim Parsons, as Sheldon Cooper, wears numerous shirts containing the number 73, this is also the year Jim was born in real life 1973, and Cooper repeatedly states that 73 is his favourite number.

The quick response (QR) code, which is visible in Stuart (Kevin Sussman)'s comic book store, contains a link to the website for the comic book centre of Pasadena.

Penny (Kaley Cuoco) was an add-on from a different sitcom concept. She had been originally envisioned as Katie, a more cynical, hard-drinking, streetwise girl who worked at a make-up salon. In the original unaired pilot, The Big Bang Theory: Unaired Pilot (2006), she was played by Amanda Walsh.

Wil Wheaton's house number (1701) is the same as the hull number of the U.S.S. Enterprise on Star Trek: The Next Generation (1987).

The opening cast shot always features the series' regulars enjoying dinner together. The opening cast credits cast shot in seasons two through four, for instance, depict Howard (Simon Helberg), Raj (Kunal Nayyar), Leonard (Johnny Galecki), Penny (Kaley Cuoco), and Sheldon (Jim Parsons) on what appears to be pizza night. However, Leonard is seen holding a plate with a white meat, and some type of vegetable, such as asparagus spears. This is apparently a reference to his lactose intolerance, which would make him averse to pizza (unless he ordered it without cheese). Amy (Mayim Bialik) and Bernadette (Melissa Rauch) were added to the shot starting in season six, even though both had been regulars on the show since season four.

Howard (Simon Helberg)'s house also appeared in Everybody Loves Raymond (1996).

Bob Newhart agreed to appear in the show on one condition, that he have a recurring role. Newhart appeared in four episodes as Arthur "Professor Proton" Jeffries.

The original working title of the show was "Lenny, Penny, and Kenny".

In tribute to Carol Ann Susi, who played Howard (Simon Helberg)'s mom, who recently passed, a small picture of her is on the side of Sheldon (Jim Parsons) and Leonard (Johnny Galecki)'s fridge. It is a small square that can be seen in episodes after her death. The picture is so small that it cannot be recognized. However, in the behind the scenes DVD feature, it is mentioned that it is her.

In the early episodes of season one, Sheldon (Jim Parsons) has two character traits that were not established right away. First, he understood the nature of romantic and sexual relationships. In the first few episodes, he chides Leonard (Johnny Galecki) for his hopes of getting into a relationship with Penny (Kaley Cuoco), often telling Leonard that he has no chance of having sex with her. Also, Sheldon understood the nature of sarcasm, as he occasionally used it himself in the early episodes. Later, his character evolved into a purely intellectual person and an emotional "man-child", who does not fully understand sex, love, or sarcasm. Second, in the early episodes, Sheldon did not use his three-times knock (knock-knock-knock "Penny", et cetera) that has become one of the character's now well known idiosyncrasies that did not begin until midway through season one.

All of the figurines and posters in Howard (Simon Helberg)'s room (and later on in his house with Bernadette (Melissa Rauch)) are female superheroes or science fiction characters. The two non-female figurine, Jabba the Hutt, has Princess Leia (in her slave girl costume) sitting in front and Jean Luc Picard sitting in the captains bridge chair. Later on in the series, they accumulate a figurine of Bernadette after the episode where he and Raj (Kunal Nayyar) got a 3-D printer.

In the original unaired pilot, The Big Bang Theory: Unaired Pilot (2006), the theme song of the show was "She Blinded Me with Science" by Thomas Dolby. Later on, however, a short MIDI rendition of the song is used as Howard (Simon Helberg)'s ringtone in The Big Bang Theory: The Lizard-Spock Expansion (2008).

While much of the show has focused on String Theory, the most often mentioned physicist is Stephen Hawking. However, the "Father of String Theory" is Leonard Susskind, who has proven Hawking wrong on several occasions.

The character Howard Wolowitz, played by Simon Helberg, is named after someone the creator of the show worked with at a computer company.

Leonard's (Johnny Galecki) last name, Hofstadter, refers to two well-known scientists: Robert Hofstadter, the 1961 Nobel Laureate in Physics, and his son Douglas R. Hofstadter, who researched consciousness and cognition, and whose best-selling book about philosophy, mathematics, puzzles, art, and music, "Gödel, Escher, Bach: An Eternal Golden Braid", was published in 1979, and won him the 1980 Pulitzer Prize for general non-fiction.

After Howard comes back from the International Space Station, Bernadette always wears the star necklace that Howard gave to her, in every episode she is seen in.

According to numerous entertainment reports, CBS has reported a large jump in the series' ratings for season six, and has attributed the increased audience to the exposure of the show in re-runs on TBS, which airs the series three nights a week in prime-time blocks of up to three hours.

Barry Kripke (John Ross Bowie) has exactly the same speech impediment as cartoon character Elmer Fudd, also a Warner Brothers character.

In every one of the main female characters' first appearances on the show, the first person to speak to them are their future mates. In the pilot, The Big Bang Theory: Pilot (2007), when Penny (Kaley Cuoco) is introduced, the first person to speak to her is Leonard (Johnny Galecki), in season three, episode five, The Big Bang Theory: The Creepy Candy Coating Corollary (2009), when Bernadette (Melissa Rauch) is introduced, the first person to speak to her is Howard (Simon Helberg), and in season three, episode twenty-three, The Big Bang Theory: The Lunar Excitation (2010), when Amy (Mayim Bialik) is introduced, the first person to speak to her is Sheldon (Jim Parsons).

While a guest on the National Public Radio program "Talk of the Nation", Mayim Bialik confirmed that the university, at which the characters attend and/or teach, is based on the California Institute of Technology (Caltech) in Pasadena. Additionally, in one episode, the character of Leonard (Johnny Galecki) stated that he worked at Caltech.

Raj (Kunal Nayyar) says that Spock had a date every seven years. He is referring to Pon Farr, the Vulcan mating cycle that occurs every seven years. Vulcans must mate in the time of Pon Farr, otherwise they will die, so Spock has a mandatory hook-up every seven years.

Sheldon (Jim Parsons)'s apartment flag that is on the refrigerator is supposed to be turned upside down only if the apartment is in distress, however, it is seen upside down in several episodes.

Both of Melissa Rauch's real-life pregnancies were written into the show. Sadly, her first ended in a miscarriage, then she got pregnant again not long after, which explains why Bernadette got pregnant again so soon after having Halley.

Amy (Mayim Bialik)'s apartment number "314" is a reference to pi, which is usually rounded off to 3.14.

As avid comic book fans, the guys frequently talk about comic book characters, or are wearing t-shirts or other paraphernalia of comics. They frequently mention DC Comics characters such as Superman, Batman, Green Lantern, the Flash, and Wonder Woman. DC Comics and this show are owned and produced by subsidiaries of Time Warner, Inc.

No two bumpers are exactly alike. Bumpers are those short videos used to separate scenes in the show.

One of the shows that survived the 2007 and 2008 writers strike. The show started in 2007, and the strike started in late 2007. This resulted in season one only being seventeen episodes.

The mother of Aarti Mann, who plays the role of Raj (Kunal Nayyar)'s sister Priya, is an obstetrician and gynecologist. In the show, Raj often states that his (and Priya's) father is a gynecologist.

The names Sheldon, Leonard, Cooper, and Hofstadter all appear on the list of Nobel Laureates in Physics. Furthermore, Sheldon and Cooper are names of physicists who won the prize for theory, and Leonard and Hofstadter are names of those who won for experiment.

Howard (Simon Helberg)'s mother was almost never seen, only heard (voiced by Carol Ann Susi), despite often being as close as the next room. Conversely, via Skype, Raj (Kunal Nayyar)'s parents are quite often seen, despite being across the world in India, except when his father visited Pasadena.

Sheldons favourite number is 73, because 73 is the 21st prime number. Its mirror, 37, is the 12th and its mirror, 21, is the product of multiplying 7 and 3... and in binary 73 is a palindrome, 1001001, which backwards is 1001001.

Sheldon (Jim Parsons) verbally reveals his and Leonard (Johnny Galecki)'s Pasadena apartment 4A's location as being 2311 Los Robles in season four, episode five, "The Desperation Emanation". In the one hundredth episode, Sheldon also reveals that their apartment building is across the street from the Colorado Avenue Chevron gas station, making their building a corner location, on the corner of Los Robles and Colorado. There are two incidences of this intersection in southern California, both located in Los Angeles County, the first one is E. Colorado Boulevard and N. Los Robles Avenue, Pasadena, California, 91101, and the second one is Colorado Boulevard and Los Robles Street, Los Angeles, California, 90041. However, 2311 Los Robles is not an address by either one of those intersections. Leonard does reveal, however, that they live in Pasadena, while declaring himself the Darth Vader of Pasadena.

Sheldon (Jim Parsons) has invented a time of day called "pre-evening". In Turkish, there's a time of day called "aksamustu", which basically means "pre-evening". In German, there is a time of day called "Vorabend", which literally translates to "pre-evening" and is most commonly used referring to TV schedules.In Bengali, there is a time called "godhuli", which also means "pre-evening". In both Czech and Slovak, there is a time of day called "podvecer", which also means "pre-evening". In Bulgarian there is a time of the day called " nadvecher" which translates to before evening.

In season six, episode ten, The Big Bang Theory: The Fish Guts Displacement (2012), Sheldon (Jim Parsons) reveals that his favorite cartoon theme song is Teenage Mutant Ninja Turtles (1987)..."turtle power!" The infectious 90's anthem was written by none other than Big Bang Theory show runner and writer Chuck Lorre.

Some of the signs in the laundry room read "No open containers on the machines", "Do not leave laundry unattended", and "Please keep your clothes on while doing laundry".

In one of the episodes, Raj (Kunal Nayyar) and Leonard (Johnny Galecki) run into Nathan Fillion. They greet him and tell him they are big fans of Firefly (2002) and Dr. Horrible's Sing-Along Blog (2008). Simon Helberg (Howard) played the character "Moist" in Dr. Horrible's.

In the German-dubbed version, the voice actor for Sheldon Cooper is the same person who usually dubs Leonardo DiCaprio.

Writer Chuck Lorre leaves a small insert called a "vanity card" at the very end of each episode. If you pause it at the end, you can read it.

Banned from China because of its "offensive content".

Leonard (Johnny Galecki)'s middle name is Leakey. Leakey is the name of a renowned family in the fields of archaeology, anthropology, and paleontology. Louis Leakey (1903-72) was a British archaeologist and naturalist, whose critical work helped to establish human evolutionary development in Africa. He also created or co-created several organizations for future research and for protecting wildlife in Africa. He also helped to establish a tradition of palaeoanthropological inquiry, and was able to motivate the next generation to continue, especially within his own family. Mary Leakey (1913-96), his wife, was a British archaeologist and anthropologist who discovered many firsts. For much of her career, she worked together with her husband in Kenya's Olduvai Gorge, uncovering relics of ancient hominines. She also developed a system of classifying the relics they found. After Louis' death, she became a leading palaeoanthropologist, helping to further establish the Leakey name and tradition with the training of her son, Richard Leakey.

In the first season finale of Young Sheldon Sheldon mentions his children that he had with Amy. However they were never mentioned on The Big Bang Theory.

In early episodes of season one, Sheldon (Jim Parsons) mentions having an older brother, in addition to his twin sister, Missy (Courtney Henggeler). In one instance, he mentions being bullied by this older brother. However, while Missy has been seen on the show, the brother was never mentioned again, even when his mother (played by Laurie Metcalff) visits. She only mentions Missy. He was mentioned in season three episode four, The Big Bang Theory: The Pirate Solution (2009), as well. In later seasons, Sheldon's brother was mentioned in season seven episode eleven, The Big Bang Theory: The Cooper Extraction (2013), season eight episode twenty, The Big Bang Theory: The Fortification Implementation (2015), season eight episode twenty-three, The Big Bang Theory: The Maternal Combustion (2015), and season nine episode five, The Big Bang Theory: The Perspiration Implementation (2015). Sheldon's older brother is shown in the Big Bang Theory spin-off, Young Sheldon (2017). His older brother makes his first appearance in season 11.

From June 2015 to June 2016, cast members Jim Parsons, Johnny Galecki, Simon Helberg, and Kunal Nayyar were the top four highest paid television actors, and actress Kaley Cuoco was the highest paid actress for the same time period.

Sheldon (Jim Parsons) only swears three times, in the first season, the fourth season, and again in the fifth season. Other times, he is shown to use either substitute words or only say the first letter.

In the same scene that Raj (Kunal Nayyar) says that "Blossom" (Blossom (1990)) would be a great addition to the Physics Bowl team, he also mentions that the "girl from The Wonder Years" was also smart. In a later episode, Danica McKellar (who played Winnie on The Wonder Years (1988)) plays a character who makes out with Raj.

Had Jim Parsons chosen to stay on, the show would have been renewed for two more seasons. This would have made the show the longest running primetime comedy beating Frasier by two seasons.

When Chuck Lorre first pitched the show to the studios, he intended for it be an adult version of the show as seen today. In the hopes of attracting as many male viewers as possible, he wrote the show with an all female cast. The female characters associated with the male main characters reflect the original characters' personas: Sheldon (Jim Parsons) was originally Missy (a tall, attractive brunette from Texas, who lacked intelligence), and lived with an older woman named Beverly (an intelligent scientist from New Jersey, who took advantage of her roommate. Penny (Kaley Cuoco) lived, as she does now, across the hall, but originally had an Indian roommate named Priya (a lawyer from New Delhi). It could be assumed that characters like Penny (Kaley Cuoco) and Amy (Mayim Bialik) might have been potential characters to add later, as well as a single male love interest in the form of unintelligent Zack (Brian Thomas Smith).

In one Halloween episode, Amy (Mayim Bialik) and Sheldon (Jim Parsons) are brainstorming couples-themed costumes, in which to dress up. Sheldon has a list of their suggestions written on a whiteboard, and while his half of the board has various genre characters listed, Amy's half has mostly romantic couples. The only exception is a listing that reads "Blossom and Joey", a reference to the title character Mayim Bialik (Amy) portrayed in Blossom (1990), and that character's brother.

Howard (Simon Helberg) is the first of the gang to get married and have a child. In real-life, Simon Helberg was the first main cast member to get married in summer 2007, just before the start of the series, and have children in 2012 and 2014.

Melissa Rauch, who plays the role of Bernadette, a Catholic, in the series, is Jewish in real-life.

While having lunch at the University canteen, or other eating scenes, characters don't actually eat most of the time. Howard (Simon Helberg) only pretends to eat the food by moving his mouth like he is chewing it, Sheldon (Jim Parsons) and Leonard (Johnny Galecki) just play with their food with fork. Amy (Mayim Bialik) and Penny are sometimes shown eating food. They only talk most of the time.

In an unaired pilot episode, The Big Bang Theory: Unaired Pilot (2006), instead of Raj (Kunal Nayyar) and Howard (Simon Helberg), Leonard (Johnny Galecki) and Sheldon (Jim Parsons) had a female companion named Gilda, who had a big crush on Leonard.

Leonard (Johnny Galecki) wouldn't eat dairy (lactose intolerent) or drink wine (sulphates) at the start of the show. Now he drinks wine all the time.

Penny (Kaley Cuoco) has never had her maiden name disclosed on-screen before. An interview with one of the writers of the show revealed that the writers are aware of this, and due to superstitious reasons are intent on not revealing it ever on-camera.

In season five, episode nineteen, The Big Bang Theory: The Weekend Vortex (2012), for some reason, Kaley Cuoco is omitted from the credits, despite appearing in the episode. In the beginning of the episode, while Leonard, Howard, and Raj are walking up the stairs, the credits start with "Starring Johnny Galecki, Jim Parsons, Simon Helberg, Kunal Nayyar..." instead of "Starring Johnny Galecki, Jim Parsons, Kaley Cuoco, Simon Helberg, Kunal Nayyar..."

Unlike most TV shows or movies, when characters in the show eat, the prop food is real. Their prop master previously aspired to be a chef and lovingly cooks every meal seen on screen.

Leonard (Johnny Galecki) is the only male lead character who hasn't taken his pants off while under the influence: Raj (Kunal Nayyar) took his off at the coffee shop while under the influence of an experimental personality altering drug, Howard (Simon Helberg) took his off on the international space station after his teammates gave him a shot for his anxiety, and Sheldon (Jim Parsons) took his off on stage while accepting an award in science after Penny (Kaley Cuoco) gives him multiple glasses of wine.

Amy (Mayim Bialik) is allergic to avocados, as revealed in season eight.

Much like the four main male characters, Amy (Mayim Bialik) and Bernadette (Melissa Rauch) wear the same style of clothing in every episode. Amy wears a knee length skirt with dark or colorful tights, a long sleeve, collared blouse with a knitted sleeveless cardigan, often underneath a long sleeved cardigan. Bernadette wears a mid-thigh length, usually floral, dress with dark or colored tights, and a short sleeved button up cardigan (although after her pregnancy starts to wear jeans and a blouse instead). Penny (Kaley Cuoco) is the only main character whose clothes do not follow a pattern.

Sheldon (Jim Parsons) once mentioned he views himself and Howard (Simon Helberg) to be acquaintances in the third season. In reality, Parsons and Helberg are good friends with each other.

In season three, episode sixteen, The Big Bang Theory: The Excelsior Acquisition (2010), Stan Lee is set to be at Stuart (Kevin Sussman)'s comic book store for an autograph signing, around the same time Sheldon (Jim Parsons) and Penny (Kaley Cuoco) are in traffic court. As Sheldon stands next to the judge at his stand, the name reads J. Kirby, a reference to Stan Lee's partner and co-creator of various Marvel characters, Jack Kirby.

Sheldon (Jim Parsons)'s routine knocking ritual was done by Penny (Kaley Cuoco) in season two, before Sheldon did it on the same episode.

While Wil Wheaton was appearing on the show, he took a photo of the set's coffee table and posted it on his much-followed blog. Among the materials on the coffee table, were copies of "Mental Floss Magazine"; "The Sandman Vol. 6: Fables and Reflections" by Neil Gaiman; a package of Pepperidge Farm Sausalito milk chocolate macadamia nut chunk cookies; a package of Red Vines; and a package of Tim's brand original-flavor lightly salted potato chips.

Katey Sagal played Kaley Cuocos mother on the show, in episode 10.1, The Big Bang Theory: The Conjugal Conjecture (2016). They also played mother and daughter on '8 Simple Rules for Dating My Teenage Daughter' (later just called '8 Simple Rules (2002). . .').

Simon Helberg's father, Sandy Helberg, guest starred on M*A*S*H (1972), in season eleven, episode eight, M*A*S*H: The Moon Is Not Blue (1982). He played Corporal Bannister, who is plagued with panic attacks whenever he is around women. Hawkeye and B.J. give him pills for confidence without telling him they are placebos. The pills work, and he becomes a ladies' man. This is the same as Raj (Kunal Nayyar), but he remedies it with alcohol.

Sometimes in the second or third floor of Sheldon (Jim Parsons) and Leonard (Johnny Galecki)'s apartment building, the caution tape on the broken elevator will come undone. Sheldon will sometimes stop and fix the tape.

In season one, episode seven, The Big Bang Theory: The Dumpling Paradox (2007), when Leonard (Johnny Galecki) talks about cutting Raj (Kunal Nayyar) in half to play Halo, Raj speaks with Penny (Kaley Cuoco) in the room. If you look at the table, you will notice that Raj does not have an alcoholic drink.

As a child, Kunal Nayyar (Raj) had a crush on Danica McKellar (Gwendolyn "Winnie" Cooper) from The Wonder Years (1988), and on this show, he actually had a relationship with her, which surprisingly made him lose all interest in her.

Sheldon (Jim Parsons)'s father's name is George, as well as his older brother's name.

Of all the primary cast members, Jim Parsons is the eldest one.

The characters often mention how Raj (Kunal Nayyar) cannot talk to women "unless he's drunk", but in fact, he only needs one sip to lose his inhibitions, as evident in many of the episodes.

All four main male characters (Leonard Hofstadter, Sheldon Cooper, Howard Wolowitz and Raj Koothrappali) appear in every episode; of those four, Leonard and Sheldon are the only ones who also appeared in the unaired pilot.

In season four, Penny (Kaley Cuoco) is going out with Zack (Brian Thomas Smith), and they attend a costume party at the comic book store, where he goes as Superman, and she goes as Wonder Woman. Kaley Cuoco briefly dated Henry Cavill, who portrays Superman in Man of Steel (2013), Batman v Superman: Dawn of Justice (2016), and the upcoming Justice League movies.

The "throw", or "blanket", on Amy (Mayim Bialik)'s couch, is the same copy as the one on Roseanne (1988). That show also starred Johnny Galecki, who plays Leonard Hoffstader on this show.

Bob Newhart reprised his role as Professor Proton in Young Sheldon (2017) - episode 1.1, Young Sheldon: Pilot (2017).

Howard is the only one you never hear vomiting. Sheldon: S3E15, S6E7, S11E11 Leonard: S2E9, S3E2 Penny: S3E2, S3E15, S5E8 Raj: S4E13 Bernadette: S10E5 Amy: S4E21, S11E11

Sheldon (Jim Parsons) and Leonard (Johnny Galecki) are atheists, yet the scientific theory that is the basis for their careers (and the show's title) "The Big Bang Theory" was actually proposed and developed by a Catholic priest, Father Georges Lemaître.

Carol Ann Susi, who voiced Howard (Simon Helberg)'s unseen mother, and Mayim Bialik (Amy Farrah Fowler) previously worked together on the Blossom (1990) episode, Blossom: The Best Laid Plans of Mice and Men (1993) as a nun and Blossom respectively.

Howard (Simon Helberg)'s mother's name is Debbie Wolowitz.

Recurring guest stars Riki Lindhome and Kate Micucci are partners in the comedy music duo Garfunkel & Oates. In their song "Handjob, Blandjob, I Don't Understand Job", they mention Mayim Bialik.

Simon Helberg (Howard) used to play Seth, a geek from Caltech, on Joey (2004). He also dated a woman named Molly, who had a squeaky voice. Howard works for Caltech, and is married to Bernadette (Melissa Rauch), who also has a squeaky voice.

Mayim Bialik, who plays the Neuroscientist Amy Fowler, is a Neuroscientist in real-life.

Sheldon has a severe disliking of birds (except for his virtual pet ostrich in World of Warcraft), however Jim Parsons is actually fond of birds, having had two parakeets as pets in his youth. Also, his first ever acting role was as a bird in an elementary school play.

Most, if not all, of the backgrounds shown while characters are driving, are shot in Pasadena. Most recognizable are Fair Oaks Avenue and Del Boulevard.

In episode 8.5, The Big Bang Theory: The Focus Attenuation (2014), Sheldon (Jim Parsons) verified that Penny (Kaley Cuoco) moved in on September 24th, the date of the premiere of the series pilot, The Big Bang Theory: Pilot (2007).

On Sheldon (Jim Parsons)'s desk there is an Android figurine, even though he uses an iPhone and an iPad.

Barry Kripke (John Ross Bowie), a recurring character on the show, appears in every season except season one.

Brian George (Dr V.M. Koothrappali) and Mayim Bialik (Amy Farrah Fowler) previously worked together on the Blossom (1990) episode, Blossom: Oh, Baby (1994) as Shakir and Blossom respectively.

Of all the characters in the show, and their wish to be superhumans, Kaley Cuoco (Penny) did have powers in another show playing a witch on Charmed (1998).

Billy Sparks, one of Sheldon's (Jim Parsons) childhood bullies is mentioned twice in the series, in episodes 3.5, The Big Bang Theory: The Creepy Candy Coating Corollary (2009), and 5.12, The Big Bang Theory: The Shiny Trinket Maneuver (2012). In Young Sheldon (2017) we get to see Billy, who is played by Wyatt McClure.

Johnny Galecki (Leonard) and Kunal Nayyar (Raj) share the same birthday (April 30), but only six years apart.

The character "Raj" was originally supposed to be named "David", but after Kunal Nayyar's audition, the name was changed to Raj.

All of the boys are interested in things like Star Wars and Star Trek, but the actors aren't huge fans of either of them in real life.

Season 1, Episode 2 (Big Bran Hypothesis): When Sheldon Cooper knocked on Penny's apartment door, it was the first time Sheldon Cooper knocked on someone's door only one time. He did not even say her name at all.

On most occasions, the gang always sit in the same places in the main apartment: Sheldon sits in his spot on the couch, Amy sits next to him in the middle, Bernadette sits next to Amy, Howard sits next to Bernadette on a chair, Penny sits on the armchair, Leonard sits next to Penny on a chair (sometimes they switch) and Raj sits on the floor.

Macaulay Culkin was asked to play the part of Leonard but he turned it down.

In the final season, Stage 25 at Warner Brothers was renamed The Big Bang Theory Stage; the fifth stage ever named after a show.

Brian George, who plays Raj's father, has also done various voice work for DC animated movies. Johnny Galecki did some voice work for Batman Beyond (1999).

The first season was originally planned to have twenty-two episodes. However, due to the 2007 to 2008 writers strike, only seventeen episodes were produced.

Jerry O'Connell, who has been hired to play Sheldon's older brother is actually a year younger than Jim Parsons, who plays Sheldon.

In August 2018 it was announced that Series 12 was to be the final season and that it is to air in 2019, 12 years after the sitcom first premiered on American television and that the 279th episode will be the last ever episode of the sitcom.

Penny (Kaley Cuoco)'s first car was a VW Golf Mk1 Cabrio.

After Carol Ann Susi died, Pamela Adlon was briefly considered to take over the role of Howard's mother before it was decided to have the character die off. Adlon would later provide the crying sounds of Hallie Wolowitz (which had a hint of Howard's mother in it).

The Chinese food containers, used in a lot of the episodes, are the same as in a lot of films, such as Night at the Museum: Battle of the Smithsonian (2009).

The wall poster in the hall in Sheldon (Jim Parsons)'s and Leonard (Johnny Galecki)'s apartment, is a chart of the electromagnetic spectrum, from the Exploratorium in San Francisco, California.

When Penny (Kaley Cuoco) first meets Leonard (Johnny Galecki)'s mother and they get talking about her dad treating her like a son, Penny says that her mother could have defended her by saying "Bob, get over it, she's a girl, move on!" This would mean Penny's father's name is Bob, however when we meet Penny's father we learn that his name is Wyatt.

Writers Chuck Lorre & Bill Prady previously collaborated on over 50 episodes of Dharma & Greg (1997), as well as the Two and a Half Men (2003)episode Two and a Half Men: A Pot Smoking Monkey (2006).

In the early seasons of the show around Christmas the gang always talk about the movie How The Grinch Stole Christmas. Leonard's mother (Christine Baranski) plays Martha May Who in How The Grinch Stole Christmas.

Casey Sander (Bernedette's dad) plays a cop. He also appeared in episodes 3.6 Sons of Anarchy: The Push (2010) & 3.12 Sons of Anarchy: June Wedding (2010) of Sons of Anarchy (2008) as a lead Sheriff, a show also based in California, but different areas. This show being in Pasadena, and Sons of Anarchy being in a town called "Charming".

Sara Gilbert (Leslie) and Johnny Galecki (Leonard) previously worked together on Roseanne (1988) as Darlene and David respectively.

"The Mystic Warlords of Ka'a" card game was created by the art department and appears in a number of episodes - 4.11 The Big Bang Theory: The Justice League Recombination (2010), 4.23 The Big Bang Theory: The Engagement Reaction (2011), 5.10 The Big Bang Theory: The Flaming Spittoon Acquisition (2011), and 6.2 The Big Bang Theory: The Decoupling Fluctuation (2012)).

In the 2011 season Leonard meets his high school bully Jimmy Speckerman. Jimmy is played by Lance Barber who is Sheldon's dad on Young Sheldon.

Howard Wolowitz drives a Mini Cooper.

In The Interview (2014), this is Kim Jong Il's favorite show. James Franco starred in The Interview and the Sam Raimi Spider-Man trilogy, which is occasionally referenced on the show.

Leonard (Johnny Galecki) and Amy (Mayim Bialik) appeared in Blossom (1990)); a show in which Bialik portrayed the title character. During this show's first season, Raj (Kunal Nayyar) suggests the gang recruit Mayim Bialik for their Physics Bowl team when Sheldon (Jim Parsons) pulls out, saying, "You know who's apparently very smart, is the girl who played TV's Blossom. She got a PhD in Neuroscience or something." Bialik soon joined the cast during the third season as Dr. Amy Farrah-Fowler, who has a PhD in Neurobiology, a.k.a. Neuroscience.

Amy (Mayim Bialik)'s door number is shown to be 314. These are the first three digits of pi.

Molly Morgan has played two roles on the show - one of Howard and Raj's goth dates, and the girl who lets them into the Escape Room.

Although Kaley Cuoco's character "Penny" is well-known to be from Nebraska, in performance Cuoco sometimes still displays a linguistic tic common to Californians: she lengthens words ending "-ing" so that they sound like "-een" and dropping the "g" (e.g. pronouncing "starting" as "starteen").

Brian Posehn (Bert) appeared in a comic book movie. He played the wedding minister in Fantastic 4: Rise of the Silver Surfer (2007).

Sheldon (Jim Parsons) tells Penny (Kaley Cuoco) in a late season one episode that Howard (Simon Helberg) had found her movie "Serial-Apist" online right after they had met her, the minute she had walked out the door. This means that they saw it between episode 1.1, The Big Bang Theory: Pilot (2007) and episode 1.2, The Big Bang Theory: The Big Bran Hypothesis (2007).

Embarrassing YouTube videos factor into several episodes: Sheldon (Jim Parsons) & Leonard (Johnny Galecki) fighting in episode 1.9, The Big Bang Theory: The Cooper-Hofstadter Polarization (2008); Sheldon's drunken acceptance speech in episode 3.18, The Big Bang Theory: The Pants Alternative (2010); Raj (Kunal Nayyar)'s way-too-revealing toast at Howard (Simon Helberg)'s stag party in in episode 5.22, The Big Bang Theory: The Stag Convergence (2012); and Howard's screaming for nine minutes aboard the ISS in episode 6.2,. The Big Bang Theory: The Decoupling Fluctuation (2012).

Season 1-2, Season 4-5 and Season 8-9 are the only examples where the ending of one season and the start of the next are on the same day, as Season 1 ended with Leonard (Johnny Galecki) and Penny (Kaley Cuoco) going out on a date, while Season 2 started with them coming back. Season 4 ended with Penny and Raj (Kunal Nayyar), while Season 5 started the same day with the guys at work. Season 8 ended with Leonard and Penny going to Las Vegas and Season 9 begins with Leonard and Penny arriving.

In episode 1.1, The Big Bang Theory: Pilot (2007), Penny (Kaley Cuoco) says she's a vegetarian, however, she is seen eating meat in subsequent episodes.

In the episode where burglars break in, Sheldon (Jim Parsons) can be seen on the couch watching a horror movie. The woman in the film says "Don't go in there, Jim!" Jim Parsons plays Sheldon.

The actor that played Leonard's bully, Jimmy in season 5 episode 11, also plays Sheldon's father on Young Sheldon.

Season one is the shortest season, with only seventeen episodes.

On re-watching the entire series run, with new information on Sheldon's upbringing via the "origin story" prequel series "Young Sheldon", some of the later TBBT running gags and story arcs become more fleshed out, and the reasonings for some of Sheldon's reasoning, behaviour and eccentricities makes more sense. One of the more intriguing ones with hindsight is how Sheldon and Penny bonded over the series. It has similat parallels with young Sheldon's bond relationship with his sassy twin sister and how he is with both of them.

Its possible that Vernee Watson's various appearances as medical staff in both Young Sheldon and The Big Bang Theory, are actually the same character in different stages of her in-universe career.

Neither an actor or the show itself were nominated for a Primetime Emmy in 2019, the year it aired its final show which is most unusual for a critically acclaimed yet popular show.

Three Nobel Prize winners made guest appearances: George Smoot, Kip Thorne, and Frances Arnold. Note: Stephen Hawking never won a Nobel Prize.

Two astronauts made guest appearances: Buzz Aldrin and Mike Massamino.

Three billionaires made guest appearances: Steve Wozniak, Elon Musk, and Bill Gates.

Two Los Angeles Lakers basketball players made guest appearances: Kareem Abdul-Jabbar and Rick Fox.

Three real life science show hosts made guest appearances: Neil deGrasse Tyson, Bill Nye, and Ira Flatow (radio).

Four Academy Award winners made guest appearances: Octavia Spencer, Keith Carradine, Kathy Bates, Billy Bob Thornton.

Five Star Trek actors made guest appearances: Will Wheaton, LaVar Burton, Brent Spiner, George Takei, and Leonard Nimoy (voice only).

Three Star Wars actors made guest appearances: James Earl Jones, Carrie Fischer, and Mark Hamill.

Two stand up comics made guest appearances: Lewis Black and Bob Newhart.

Other science fiction actors who made guest appearances were: Summer Glau, Sarah Michelle Geller, Eliza Dushku, Katie Sackhoff, Christopher Lloyd, and Nathan Fillion.

The following actors who had starred in other situation comedies made guest appearances: Adam West, Bob Newhart, Katey Sagal, Sarah Gilbert, Christine Baranski, Laurie Metcalf, Charlie Sheen, Jack McBrayer, Jane Kaczmarek, Danica McKellar, Judd Hirsch.

In the unaired pilot episode, The Big Bang Theory: Unaired Pilot (2006), Sheldon (Jim Parsons) is portrayed as having a lot of qualities he didn't have in the finished script. He was able to understand sarcasm, and wasn't as condescending as normal. He also was revealed to have engaged in sexual relations.

The pilot episode, The Big Bang Theory: Pilot (2007), was viewed by 9.52 million people and had a rating of 3.7 (adults 18-49).

The pilot that went to air (The Big Bang Theory: Pilot (2007)) was not the original pilot. The first pilot that was made (The Big Bang Theory: Unaired Pilot (2006)) was not approved.

In 2017, Sheldon Cooper got his own spin-off series which is a prequel to the sitcom entitled "Young Sheldon". The prequel series follows the irritating theoretical physicist when he was a child genius living in Texas and his family's struggles to deal with him. As of 2018, Sheldon Cooper is the only character in the sitcom to get his own spin-off.

The words to Sheldon's favourite song are as follows. "Soft kitty, warm kitty. Little ball of fur. Happy kitty, sleepy kitty purr, purr, purr." It's actually based on an Australian nursery rhyme that was featured on the Australian children's show "Play School".

Currently (November 2016), the show broadcasts over five channels in South Africa (The most of any show at any given time), the latest episodes on M-Net, and reruns on VUZU, VUZU AMP, M-Net Family, Comedy Central, and SABC3.

Brian George's earliest recurring role in a television show, was as a police detective on The Edison Twins (1982), a Canadian series about a pair of teen scientists who solved mysteries.

In season 4 episode 5 "The Desperation Emanation", Raj says he's dating a deaf girl, meaning to date he's dated two deaf girls and two red headed girls named Emily.

The UK's Channel Four and E4 appear to have slightly edited dialogue from certain episodes as the audience laughter abruptly starts, stops, or jumps, suggesting bad "cut and shunt" editing, not consistent with the professional editing standards Warner Brothers Television usually releases. This is result of UK Broadcast Standards compliance edits made, as the two channels show the program multiple times across daytime, afternoon, evening, and nighttime slots.

The name Hofstader was used before by Chuck Lorre, in episode 2.21, Dharma & Greg: It Never Happened One Night (1999), of Dharma & Greg (1997), where Kitty Montgomery, played by Susan Sullivan, receives the "Hofstader award".

The pilot episode was taped on Valentine's Day, and the series finale was taped on Kunal Nayyar and Johnny Galecki's birthday.

Mark Cendrowski was nominated for the 2018 Emmy Award in the Outstanding Directing For A Comedy Series category for The Big Bang Theory: The Bow Tie Asymmetry (2018), but lost to Amy Sherman-Palladino for The Marvelous Mrs. Maisel: Pilot (2017).

Every season premiere episode was directed by Mark Cendrowski, except of the pilot, which was directed by James Burrows.

Any time the characters have food they rarely eat. They simply play with the food.

Sheldon (The Big Bang Theory: The Cooper Extraction (2013)) first mentions his twin sister Missy who works as a hostess at Fuddruckers in episode 1.1, The Big Bang Theory: Pilot (2007). She later appears in episode 1.15 The Big Bang Theory: The Pork Chop Indeterminacy (2008), and is heard screaming in episode 7.11 The Big Bang Theory: The Cooper Extraction (2013).

Season 2 ending and Season 3 beginning are 3 months apart, Season 3 ending and Season 4 opening are 4 months apart, Season 4 ending and Season 5 opening are also on the same day, with Season 4 ending with Penny (Kaley Cuoco) and Raj (Kunal Nayyar) in bed together while Season 5 begins just a few hours after that. Season 5 ends with Howard (Simon Helberg) in space while Season 6 starts a week after his launch. Season 6 ends with Leonard (Johnny Galecki) going to the North Sea expedition while Season 7 starts 4 months after his departure. Season 8 starts 45 days after Sheldon (Jim Parsons) departs on his soul-searching train trip.

Sheldon, Howard, Leonard all use Windows based laptop computers.. Raj uses a MacBook Pro laptop and there's Mac computers in all their well as Amy's. The only time you see any Mac being used, is either when Raj uses his laptop (the logo of which is covered by bullet hole stickers), or at Howard's or Amy's lab (the logos also covered by grey circle stickers). They also each have always had an iPhone. Not one character has ever used an Android or any other phone.

Sheldon Cooper & Amy Fowler. In the 1952 classic western "High Noon". Gary Cooper marries Amy Fowler (Grace Kelly)

The "Dr. Stephanie" (Sara Rue) trilogy played out over the following episodes: S02E08: The Big Bang Theory: The Lizard-Spock Expansion (2008) - Howard (Simon Helberg) tries to seduce Stephanie by showing her the Mars rover, however Stephanie ends up interested in Leonard (Johnny Galecki) S02E09: The Big Bang Theory: The White Asparagus Triangulation (2008) - Sheldon (Jim Parsons) worries that Leonard and Stephanie's relationship is not progressing well enough and goes to Penny (Kaley Cuoco), Raj (Kunal Nayyar), and Howard for advice on how to stop Stephanie inevitably ending the relationship with Leonard - Leonard and Stephanie are officially in a relationship by the end of this episode, in part, thanks to Sheldon S02E10: The Big Bang Theory: The Vartabedian Conundrum (2008) - Stephanie has moved into the apartment without Leonard even noticing; Leonard wants to slow things down with Stephanie.

In season four, episode five, The Big Bang Theory: The Desperation Emanation (2010), Raj (Kunal Nayyar) mentions that he's dating a deaf chick. He then goes on to date a deaf woman in season five, episode four, The Big Bang Theory: The Wiggly Finger Catalyst (2011).

Sheldon (Jim Parsons) was born in Texas. In season two, Leonard (Johnny Galecki)'s girlfriend Stephanie (Sara Rue) mentions that she did her medical internship in Texas.

Episode 1.1, The Big Bang Theory: Pilot (2007), establishes that Leonard (Johnny Galecki) is lactose intolerant and cannot process corn.

In episode 1.1, The Big Bang Theory: Pilot (2007), Sheldon (Jim Parsons) seems to use and understand sarcasm, however in future episodes, it is well established he does not understand it.

In the episode "The aconvention Conundrum", James Earl Jones invites Sheldon and his friends to Comic-Con as his guests. In a much later episode, Leonard is angry that Sheldon spent an entire day with JEJ and didn't tell any of them, meaning he never told them about the chance to go to Comic-Con because it means he would have had to spend a night in Tijuana with the actor.

Howard (Simon Helberg) takes Sheldon (Jim Parsons) to a dancing class in episode 1.3, The Big Bang Theory: The Fuzzy Boots Corollary (2007), however, in a later episode, he says he does not enjoy dancing and never will. Then, in the fourth season, he reveals that he can do formal dances such as the Waltz.

Writers Steve Holland & Steven Molaro previously collaborated on the iCarly (2007) episode, iCarly: iWant More Viewers (2007).

In season one, episode thirteen, The Big Bang Theory: The Bat Jar Conjecture (2008), while discussing who to recruit to their quiz team, Raj (Kunal Nayyar) mentions that they should get TV's Blossom on their team. The lead character on the show Blossom (1990), Mayim Bialik (Amy), went on to appear on The Big Bang Theory in the final episode of season three, The Big Bang Theory: The Lunar Excitation (2010), and has been a regular cast member since season four.

In episode 1.1, The Big Bang Theory: Pilot (2007), Leonard (Johnny Galecki) mentions that his grandmother was there for Thanksgiving, had Alzheimer's and got naked. Later it is established that he was from New Jersey, making his ill grandmother traveling all the way across the country implausible.

Eight episodes have a "Previously on The Big Bang Theory" review of past events. The first being episode 3.1, The Big Bang Theory: The Electric Can Opener Fluctuation (2009), which summarises episode 2.23, The Big Bang Theory: The Monopolar Expedition (2009) and it is narrated by Kaley Cuoco. The other seven are episodes 4.16 The Big Bang Theory: The Cohabitation Formulation (2011), 5.1 The Big Bang Theory: The Skank Reflex Analysis (2011), 5.24, The Big Bang Theory: The Countdown Reflection (2012), 6.1 The Big Bang Theory: The Date Night Variable (2012), 8.1 The Big Bang Theory: The Locomotion Interruption (2014), 9.1 The Big Bang Theory: The Matrimonial Momentum (2015), and 9.16 The Big Bang Theory: The Positive Negative Reaction (2016).

The theme song does in fact say that the universe is 14 billion years old, "then nearly 14 billion years ago expansion started, wait!". It's just kind of hard to distinguish the B and the M.

At 12 seasons and 279 episodes, this is the longest running primetime comedy series. The longest running comedies before this were M*A*S*H and Frasier, they both ran for 11 seasons. In third is Friends, which ran for 10 seasons.

Sheldon's week is as follows - Monday is Wii Bowling night Tuesday is hamburger night Wednesday is Halo night Thursday is pizza night Friday is vintage video game night Saturday is laundry night It is never mentioned what he does on Sundays, but since he grew up in a strict Christian household, it can be presumed that Sunday's are a "day of rest" for him.

Jim Parsons is the only main cast member to win an Emmy, Golden Globe and Peoples Choice Award for his performance on the show. The show itself won the Peoples Choice Award for Favorite Network TV Comedy/TV Comedy a total of seven times, the most for any network comedy series.

People who have taken out restraining orders against Sheldon: Carl Sagan, Leonard Nimoy, Stan Lee, Bill Nye.

Continuing the connections between Roseanne and Big Bang Theory, (Johnny Galecki, Laurie Metcalf, Sara Gilbert), is Meagan Fay. Maegan Fay's claim to fame was playing Kathy Bowman for two seasons on Roseanne, playing Barr's snooty next-door neighbor. Meagen Fay also played Kaley Cuoco's mother in the movie Kaley produced "Authors Anonymous" besides playing Bernadette Rostenkowski's mother on Big Bang Theory.

It can be argued that Raj's parents marriage began to deteriorate in the episode "The Wiggly Finger Catalyst", when Raj's father makes him choose between love and money, and Raj chooses love, and his father says "You're an idiot!! Love doesn't last!", and then his mother gives him a very evil glare. Before that every conversation he had with them over video chat, they were very happy, but every video chat after that, they're very passive aggressive each other, until they eventually get divorced.

Interesting fact. Even though. Leonard's apartment and Penny's apartment have doorbells no one uses them.

It is interesting everyone basically just walks into Leonard's apartment without knocking. However when anyone goes to Penny's apartment they always knock.

Leonard's apartment has a lot of appliances however the only one consistently used is the toaster. They never use the frying pans.

The majority of motorway scenes where Leonard is driving there is usually a silver BMW Z3 driving behind his car

In the episode "The Zazzy Substitution", Amy points out that the Danish were the ones who invented the food danish. But in the episode "The Imitation Perturbations", Sheldon says that they were imported by Austrian bakers during a labour strike in 1800's.

Raj is the only character who was never seen with a girl in the opening sequence.

The elevator in the apartment building wasn't finally repaired until the penultimate episode, "The Change Constant".

The phone on the end table between the couch near Sheldon's "spot" and the stationary chair is a V-Tech LS6195. It has never been used in the entire series.

People mistake the theme song as saying "nearly 14 million years ago expansion started, wait", when it actually says 14 billion.

There are two shots in the whole series of the apartment buildings stairs facing downward, in the episode "The Allowance Evaporation", when Amy gets mad at Sheldon, and in "The Big Bran Hypothesis", when they are trying to lift Penny's delivered furniture upstairs.

Stuart Bloom's full name isn't revealed until season 7, episode 18 "The Mommy Observation".

Howard's mom was played, (voiced), by Carol Ann Susi. She made 3 appearances on Kolchak the Night Stalker with Darren Mc Gavin as Monique.

The theme song line "autotrophs began to drool" , rather than a joke, might reflect a fairly common mistake. 'Troph' refers to source of nourishment, 'autotroph' means self feeding or photosynthetic. 'Trop' refers to movement, chemotrops move toward specific chemicals and phototrops move toward light. Some folks, even in the sciences, mix a nonexistent word 'autotrop' (suggesting self moving) and 'autotroph' to imply animal.

Of the three main characters who marry, Sheldon seems to be the only one whose significant other is in his league.

Brian Posehn plays Bert, a doctor of Geology, on Big Bang Theory. He has a reoccurring role where he plays biology/earth science jr high teacher on New Girl.

Two things never happen in the entire series: Penny's maiden name is never revealed, and Raj never gets married.

As at 2018 Penny (Kaley Cuoco) is the only remaining main character whose surname has yet to be revealed. However, in the season nine premiere, she took Leonard (Johnny Galecki)'s surname of Hofstadter.

In the one hundredth episode (5.13 The Big Bang Theory: The Recombination Hypothesis (2012)), where Leonard (Johnny Galecki) asks Penny (Kaley Cuoco) out again, Penny is wearing the same shirt she wore in the pilot. This was probably to represent Leonard falling in love again with the same girl he did one hundred episodes before.

Howard (Simon Helberg)'s mother's voice was heard throughout the show, but her face has never been actually seen on-screen (she appeared very briefly on-screen in the season five finale, as the camera pans up from the rooftop, but her face was still never shown). She died after the actress who played her, Carol Ann Susi, died of cancer.

Chuck Lorre stated in an interview that Penny (Kaley Cuoco)'s surname is Barrington. However, this was never revealed in the series.

Carol Ann Susi, who plays Howard (Simon Helberg)'s unseen mother, died from cancer on November 11, 2014. Her character was subsequently written out of the show.

The cast and crew have performed two "flash mobs" to audiences after taping an episode, one to Carly Rae Jepsen's "Call Me Maybe", and the other to Mark Ronson's "Uptown Funk".

Leonard (Johnny Galecki) is the only regular male character who wears glasses. His wife Penny (Kaley Cuoco) is the only regular female character who doesn't wear glasses.

Of all of the main characters, Leonard (Johnny Galecki) and Penny (Kaley Cuoco) have had the same amount of relationships over the course of the show (Penny: Kurt, Zack, Stuart, Mike, and of course Leonard) (Leonard: Penny, Dr. Elizabeth, Priya, Leslie, and Stephanie), then Raj (Kunal Nayyar) (Lucy and Emily), Bernadette (Melissa Rauch) (Glenn and Howard), and Howard (Simon Helberg) (Leslie and Bernadette). Amy (Mayim Bialik) (Dave and Sheldon) and Sheldon (Jim Parsons) (Ramona and Amy).

In season six, episode two, The Big Bang Theory: The Decoupling Fluctuation (2012), Amy (Mayim Bialik) mentions that she and Sheldon (Jim Parsons) will be getting married in exactly four years. At the end of the season ten finale, Sheldon proposes to Amy, making this to be a somewhat valid prediction.

Raj (Kunal Nayyar), Priya (Aarti Mann), Leonard (Johnny Galecki), and Bernadette (Melissa Rauch) are the only characters to have had both of their parents introduced in the series, prior to the season ten episode aired on Monday September 19, at 8 p.m. Eastern and 7 p.m. Central. In this episode, both of Penny (Kaley Cuoco)'s parents were introduced together.

In the season five finale, The Big Bang Theory: The Countdown Reflection (2012), when Howard (Simon Helberg) and Bernadette (Melissa Rauch) are getting married, during the wedding, Raj (Kunal Nayyar) talks without drinking any alcohol, even though there is Amy (Mayim Bialik), Penny (Kaley Cuoco), and Bernadette (Melissa Rauch) in the same place.

Most of the characters have evolved since their first appearance. Sheldon (Jim Parsons): He gains more feelings about women, and even gets physical with Amy (Mayim Bialik), and tells her he loves her. Howard (Simon Helberg): He is less creepy than he was in the first season, and finally settled down. Raj (Kunal Nayyar): He can now speak to women without being drunk. Amy (Mayim Bialik): She is less like Sheldon, and not as robotic.

The guys and their relationships go in the following order; Howard is the first to get married and the first (and technically only one) in the series to have children, Leonard is next and he and Penny announce they're expecting in the series finale, Sheldon marries Amy but don't mention children in the series (though Sheldon mentions he and Amy eventually have kids in "Young Sheldon"), and finally Raj almost gets married but decides against it due to him rushing into it with Anu, the girl his father sets him up with.

Here is a problem. You see the abbreviations d and l. This is redundant. Dialog is language!