Throughout the first season, "The Observer" could be spotted on other FOX programming such as in the audience of American Idol (2002), or on the sidelines of NFL and NASCAR events.

Jasika Nicole has said in several interviews that the Alternate Universe version of her character, Astrid, is on the Autism spectrum (or has high-functioning Asperger Syndrome), which accounts for her statistical prowess and her disinclination to make eye contact with others. Nicole has said that her inspiration for the character comes from her own sister, who is also on the spectrum.

For the first season, each episode of this show ran from about forty-nine to fifty-one minutes in length. This is in contrast to the typical forty-two to forty-three minute length of a one-hour drama. This was an experiment by FOX to see if viewers are more likely to tune in if there are fewer commercials.

In season one, episode nine, "The Dreamscape", the victim that fell from the Massive Dynamics building had a flight booked on Oceanic Air to Omaha, the same airline featured in Lost (2004). Oceanic Air is a fictional airline used in several Hollywood productions where bad things happen to aircraft. (Real airlines are understandably reluctant to be associated even with fictional crashes and hijackings.) It goes back at least to Executive Decision (1996) with Kurt Russell and Halle Berry.

Every time the title sequence is red, the episode takes place in the parallel universe, because red is opposite to blue on the color wheel, which is the color the sequence usually is.

In season one, the Fringe team has several encounters with a man named David Robert Jones. In the second season, they fight a visitor from the alternate universe named Thomas Jerome Newton. "David Robert Jones" was David Bowie's real name, and "Thomas Jerome Newton" was the name of the character he played in The Man Who Fell to Earth (1976).

In September 2008, Joshua Jackson had to be rushed to the hospital, when during a stunt, a copper wire was shoved up his nose and hit a vein.

Unlike other actors who've gone bald for their characters (such as Michael Rosenbaum's decision to shave his head to play Lex Luthor in Smallville (2001)) Michael Cerveris, who plays "The Observer", was already shaved bald before being cast. He first shaved his head in 1993 while playing Tommy in the Broadway musical "The Who's Tommy", because he wore a wig in that show, and found it more comfortable to put the wig over a shaved head. However, Cerveris does have eyebrows. The Fringe (2008) Make-up Artists only make it appear that he does not.

Walter's Harvard lab, out of which the Fringe team work, is room number B314.1; 3.141 is the value of Pi in mathematics.

During the DVD commentary for season two, episode twenty, "Brown Betty", featuring Effects Supervisor Jay Worth, co-Producer Tanya Swerling, Composer Chris Tilton, and co-Music Supervisor Billy Gottlieb, they discuss the fact that every episode of this show includes an "Easter egg", a reference that foreshadows some element of the next episode.

In some of the episodes, you'll find a coffee mug with a kangaroo for the handle. That coffee mug came from John Noble's house, letting the viewers know that he is from Australia.

There have been several indications that in the alternate universe, Humphrey Bogart was not a movie star, or at least did not have the same career he had in the real world: Lincoln identifies Cary Grant, not Bogart, as the actor who plays the Sam Spade role in The Maltese Falcon (1941), and Fauxlivia identifies Ronald Reagan, not Bogart, as the male star of Casablanca (1942). Ronald Reagan was originally considered for the part of Rick in Casablanca (1942) before Bogart was given the part.

John Noble is one of the only cast members who appeared in all one hundred episodes.

In the alternate reality, Eric Stoltz is billed as the star of Back to the Future (1985). Eric Stoltz was originally cast in the role before being replaced by Michael J. Fox.

The makers of the show enjoyed season two, episode twenty, "Brown Betty", so much, that they decided to always make the nineteenth episode of each season special. Hence, the animated episode in season three, or the flash-forward one in season four.

Peter and Walter are left handed.

When they started to write the alternate universe Olivia character, the show's writers referred to her among themselves as "Bolivia", because they considered the original Olivia to be the one from the "A-plot", and so the alternate universe Olivia was from the "B-plot", "B-Olivia" (Bolivia is also the name of a country in South America). However, this name did not catch on amongst the fans, who quickly started calling her "Fauxlivia" (from the French word for "false") instead.

When the adult Peter first arrives in the alternate universe, slightly altered DC comic book covers can be seen mounted on a wall. One is a crossover issue starring Red Lantern and Red Arrow, in our universe, both characters are associated with the color Green. The other is what appears to be a copy of a Superman comic, "The Man of Steel Returns", in our universe, this is a Batman title called, "The Dark Knight Returns". Superman's distinctive red cape can be seen in place of Batman's black cape on the shadowy hero. Both covers have distinctive red colors not found in our universe versions. Red is the color code for this show's alternate universe.

In several episodes, the F.B.I.-issue SUV that Agent Olivia Dunham drives, can be seen to have the registration plate 1-C3P0-1. Creator J.J. Abrams was the Director for Star Wars: Episode VII - The Force Awakens (2015). The Star Wars saga famously featured the droid C-3P0.

In season two, episode eighteen, "White Tulip", there are two F.B.I. SUV's. One license plate reads "1C3PO1", and the second read "1R2D21", referring to the two main droids from the Star Wars saga.

Season four shows the title sequence in yellow. This is right in between green and red on the color wheel. Green is for the normal universe, and red is for the alternate.

The pilot was filmed in Ontario, Canada, but the rest of the first season was shot in New York City. Production moved to Vancouver, British Columbia for season two.

Although Walter usually gets Astrid's first name wrong, he always gets her last name right.

Many of the "in between images" include the golden ratio (the larger quantity is equal to the ratio of the larger quantity to the smaller one), the golden spiral, or the Greek letter Phi, which is the mathematical symbol for the golden ratio.

Most outside shots of the supposed Harvard University buildings are pictures of Yale University buildings. Some example shots are: Lanman-Wright Hall, Durfee Hall, and the Yale Station post office (as seen from Old Campus) and Calhoun College (as seen from Cross Campus).

Jasika Nicole said her favorite episode was season four, episode eleven, "Making Angels", where she is visited by the alternate Astrid.

Anna Torv and Mark Valley were married from 2008 to 2009, around the time season one was airing. Valley plays Torv's partner and lover in season one.

Edward Markham, the bookstore owner with a burgeoning collection of esoteric titles, was likely named after the poet Edwin Markham, who amassed a personal library of over fifteen thousand books by the time of his death.

"Massive Dynamic", originally "Massive Dynamics", plays a key role in this series. This fictional corporation had been mentioned a few months before this series' debut, in leaked casting sheets for Transformers: Revenge of the Fallen (2009).

There have been several indications that in the alternate universe, The West Wing (1999) did not end with its seventh season, but is in fact still running, albeit with a Barack Obama-like Presidential character (instead of President Santos, played by Jimmy Smits, whose inauguration ended the real show). The real The West Wing (1999) was originally supposed to have a black President, but Sidney Poitier turned down the role that eventually went to Martin Sheen.

The Bank of America tower in Manhattan was used as the exterior shot of the Boston Federal building. J.J. Abrams also used this building as the C.I.A. Headquarters in Alias (2001).

In an episode while looking for Dr. William Bell's (Leonard Nimoy) copy of "ZFT", it shows a small collection of books, and one of the books has "Dr. Spock" written large on the binding. A reference to Nimoys' famous role as Mr. Spock in the Star Trek franchise. However, "Dr. Spock" was a real-life child psychologist, and Nimoy's fictional character was "Mr. Spock".

On a map on the wall in Walternate's office, the western half of California is missing. In real-life, the state is bisected by the San Andreas fault, running from north to south.

Astrid (Jasika Nicole) has a Bachelor of Arts degree (a double major in music and linguistics) from Haverford College, a real, prestigious, private liberal arts college near Philadelphia, Pennsylvania.

In season three, episode ten, "The Firefly", Christopher Lloyd (Doc Brown from the Back to the Future trilogy) plays a character who sees his son who had died in 1985...the year of the "present" timeline in the Back to the Future trilogy. "The Firefly" revolves around "The Observer" explaining to Walter that their actions in 1985 had altered reality, a science fiction theme common to the Back to the Future trilogy. In the same episode, Walter puts on 3-D wire rimmed glasses and says to Astrid that he got the "look" from an old friend, Dr. Jacoby from Washington. Doctor Jacoby was a character who wore the same glasses on the television show, Twin Peaks (1990), which was set in Washington. (Possibly a stretch, but, Christopher Lloyd's character is Roscoe Joyce and his son's name is Bobby. Bobby was a charcter on Twin Peaks (1990) played by Dana Ashbrook, who appeared in nine episodes of Dawson's Creek (1998), which starred Joshua Jackson (Peter on this show).)

At the start of the second season, a new character, Junior FBI Agent Amy Jessup (Meghan Markle), was introduced. She was a major focus in the plots of the season's first two episodes (a piece on Buzzfeed said that Jessup was introduced to be a "a new governmental foil for Olivia Dunham to spar with, and a potential love interest for Peter Bishop"), but after that, she was never seen or mentioned again. In 2014, Markle shared her theory about what happened to her character: "That role was always crafted as being recurring or a series regular. Akiva Goldsman was directing those first two episodes, and he'd been doing all that DaVinci Code stuff [Goldsman wrote the screenplays for 2006's The Da Vinci Code and 2009's Angels & Demons], so this idea of how science and religion coexist was very much in the zeitgeist. I think it ended up being a storyline that scared off the studio or network, so Amy just evaporated. I was intending on being [in Vancouver, where Fringe filmed] for a while, but she was just phased out. Amy maintains this air of mystery and I kind of think fans assumed she was going to pop back up again--like Amy was the one behind all of the Fringe mysteries," she said, laughing. Markle went on to play a lead role on seven seasons of "Suits"; in 2018 she married Prince Harry of Britain.

Lance Reddick (Agent Phillip Broyles ) and Kirk Acevedo (Agent Charlie Francis) appeared on Oz (1997).

In season four, episode nineteen, "Letters of Transit", there is a reference to Star Wars, when Walter Bishop says to the security guard, "these are not the droids you are looking for", which is a line Sir Alec Guinness (Obi-wan Kenobi) said in Star Wars: Episode IV - A New Hope (1977).

To promote this series in Germany, channel ProSieben created a couple of fake breaking news that were played during commercial breaks, which featured alleged on-location footage. To create a sense of authenticity, the channel used both the studio and the newsreader that were already familiar to the regular audience. The "on-location" footage was taken from the series (from the episodes Fringe: The Same Old Story (2008) and Fringe: The Dreamscape (2008)), showing gruesome scenes. At the end of each "breaking news", the channel's announcer revealed the show's title and the premiere date. ProSieben's method was met with heavy criticism, not only because the clips from the episodes were presented in a sensational fashion, but also because they were disguised as part of a serious news broadcasting. Additionally, the promos also aired in the afternoon, where it is prohibited under the German law to show content that is inappropriate for people under 16. Because of that, the channel was fined 3.500 Euros, charged by the German Commission for the Protection of Minors in the Media, as the channel had violated the youth protection policy.

In its original television run, this show was aired on FOX. In 1985, FOX was acquired by News Corporation, a holding company controlled by Australian media mogul and billionaire Rupert Murdoch. From 1967 to 1999, Murdoch was married to his second wife, Anna Maria Torv Murdoch (now Mann). Anna is a paternal aunt and the namesake of Anna Torv, the actress who plays F.B.I. Agent Olivia Dunham on this show. Rupert Murdoch's three children with Anna Maria Mann (Elisabeth, Lachlan, and James Murdoch) are the actress's first cousins.

The number 47 appears frequently throughout the series. This is due to J.J. Abrams directing and producing the Star Trek reboot movies (as well as show co-Creators and Writers Alex Kurtzman and Roberto Orci writing for them). It is well-known in Trek lore that the number 47 appears frequently throughout the different series (from Star Trek: The Next Generation (1987) and forward). The story behind that is Joe Menosky (Writer from Star Trek: The Next Generation (1987) on) began inserting it, because at his alma mater, Pomona College, 47 was something of a superstition. It goes back to 1964, where it originated partly in a joke-proof from math professor Donald Bentley that all numbers were equal to one another (he chose 47), and partly from the observation by a few students that the number 47 occurred more often than you'd expect it to.

Blair Brown starred in a movie which included the use of a sensory deprivation tank and hallucinogenic drugs, Altered States (1980), with William Hurt.

In the season three opener, "Olivia", the alternate universe version of the Department of Defense Hospital building is a clip of a building at the University of Houston.

In season one, episode eleven, "Bound", Walter expounds on the "definitive spiderweb look" of a projected image he describes as "simian hemorrhagic fever". The image displayed is clearly (and apparently correctly) labelled Leptospira sp., a spiral-shaped bacterium. Simian hemorrhagic fever is caused by the Simian hemorrhagic fever virus.

Astrid Farnsworth's Agent's ID is JH12402.

Leonard Nimoy (Dr. William Bell) and Christopher Lloyd (Roscoe Joyce) appeared in Star Trek III: The Search for Spock (1984).

In Germany, Lance Reddick was often confused with Germany's Next Topmodel (2006) judge Bruce Darnell. In fact, not only were both men born in the US, they also have indeed a striking resemblance to each other, down to the bald head and the stature. This led many viewers to believe that Darnell was acting in this show.

The ZFT manifesto name "destruction through technological advancement" bears strong resemblance to the Unabomber manifesto which contains themes if the destruction of humanity through the domination of our lives by technology.

"The Observer" could be spotted in many season one episodes before he was officially introduced as a character: Episode one, "Pilot": Walking past Massive Dynamics in the intro shot to that corporation. Episode two, "The Same Old Story": At the counter in the hospital. Episode three, "The Ghost Network": In a couple of shots (one is a reflection) on the train. Episode four, "The Arrival": Featured several times. Episode five, "Power Hungry": Getting off the doomed elevator as it fills up. Episode six, "The Cure": In the country club watching Dunham's conversation with (bad guy), two shots, one long, then he crosses directly behind the two as they converse. Episode seven, "In Which We Meet Mr. Jones": In the German airport near the ticket counter. Episode eight, "The Equation": Outside, under a tree when Dunham takes a cell call outside the house they're searching.

In the alternate universe, a radio broadcast indicates that President Kennedy was not assassinated. There is also a photo of a gray haired J.F.K. on Walternate's desk.

Series villains David Robert Jones (Jared Harris) and Thomas Jerome Newton (Sebastian Roche) share several similarities; The characters are seen "reforming" in their introductions, Jones via teleportation, Newton with his head being re-attached. Their names are derived from David Bowie pseudonyms, the former being his birth name, and the latter, a film character he portrayed, and both have served under a higher power, Jones with Dr. William Bell in season four, and Newton with Walternate in seasons two and three.

In season two, episode eight, "August", at the end, when August is dying, his words foreshadow October's actions later on to save the Observer Child from season one.

During the second season, when Olivia is having trouble readjusting to life in her universe after Dr. William Bell violently pulled her into and then back out of the alternate universe, Nina Sharp suggests she should visit Sam Weiss, an unorthodox therapist who once helped her. The first several times that Olivia visits Sam, who works in a bowling alley, the P.A. system there is playing an instrumental version of the Steve Winwood song "Can't Find My Way Home", a nod to the reason for Olivia's troubles.

As of Season 4, Anna Torv has portrayed more than one character: Olivia, William Belle, Bolivia, Alternate Future Olivia and Brown Betty Olivia.