Al's cigar was the idea of Dean Stockwell, who said it was "a good way to get free cigars for five years."

Scott Bakula was the first actor cast, and thus was asked to read with actors under consideration for the role of Al Calavicci. Bakula immediately felt a connection with Dean Stockwell during his audition, and lobbied the producers to cast him as Al Calavicci.

Scott Bakula ad-libbed the line "Oh boy!" at the start of the first episode. The producer liked it so much, that it became the signature final line of each episode, as Sam finds himself in a new body.

Scott Bakula did his own singing in episodes in which Sam leaped into musical performers, or was otherwise called upon to do. Prior to his work on television, Bakula had done extensive work in musical theater.

Almost immediately after the series was cancelled, producers announced plans to continue with a television series (or perhaps theatrical movies). Scott Bakula expressed optimism in the projects, and stated that he and Dean Stockwell wanted to continue in their roles. Nothing came of the plans, the closest being an announced movie for the Syfy Channel in the early 2000s, which was never produced.

Sam Beckett leaped into the year 1957 seven different times, which made it the most leaped into year during the series' entire run.

In an interview conducted shortly after the series ended, Scott Bakula was asked if there were any particular historical figures or events he would have liked to see Sam involved with. Bakula said he would have liked to have done something with the Kennedys unrelated to the assassination or relationship with Marilyn Monroe.

The character Sam Beckett was ranked #12 in TV Guide's list of the "25 Greatest Sci-Fi Legends" (August 1, 2004 issue).

According to Dean Stockwell, his friend Dennis Hopper advised him not to take a role on television so soon after being nominated for an Academy Award (Best Actor in a Supporting Role for Married to the Mob (1988)). Stockwell took the role anyway, and was nominated for four Emmys, and four Golden Globes (and won one in 1990), for his role as Al.

Quantum Leap (1989) came close to being cancelled in its third season, due to low ratings. However, a letter writing campaign helped save the series, and enabled it to continue for two more years.

Season five, episodes one and two, "Lee Harvey Oswald Parts 1 and 2", were written by Donald Bellisario after overhearing his children talking about the movie JFK. He always believed that Oswald was the lone gunman. He based this on a conversation with Oswald in the late 1950s, when both were in the Marines. The meeting was part of the second part of the episode, with Matthew Charles Nelson playing Bellisario.

There were several ideas for episodes which ultimately were never used. One had Sam leaping in as Robert F. Kennedy. Another idea would involve an animated episode. The producers even toyed with the idea of leaping Sam in as a baby (this was to be the story of the fourteenth issue of the Quantum Leap comic book, but production ended after issue #13). Also, Writer and Producer Donald P. Bellisario wanted to do an episode where Sam leaps in as Thomas Magnum (from Magnum, P.I. (1980)). It is unclear why that episode never materialized, although in an earlier episode, a character is seen watching Magnum, P.I., thus establishing that series as fiction within the Quantum Leap universe.

Donald P. Bellisario's favorite of all of his television series.

Ranked #15 in TV Guide's list of the "25 Top Cult Shows Ever!" (May 30, 2004 issue).

Though no special mention is made during the series, with the exception of Gooshie, Project Quantum Leap is run almost entirely by women. They include: Dr. Donna Eleese, Sam's wife, also a physicist; Dr. Beeks, a medical technician; Teena Martinez, Al's girlfriend and assistant programmer; an unnamed military envoy; and, though she is never seen, Dr. Sammy Jo Fuller, Sam's daughter sired during a leap, also a physicist. In addition, Ziggy, the sentient computer that controls the project, displays female characteristics.

Sam Beckett leaped into every year from 1953 from 1987 at least once except for 1977, 1984 and 1986. Sam also leaped into 1862 and 1945, the only times that he has leaped out of his lifetime.

Deborah Pratt, the series Narrator, and voice of Ziggy, also wrote and Executively Produced the series. She was married to Donald P. Bellisario when the series aired.

Donald P. Bellisario established Sam Beckett's birth year 1953 by reversing digits of his own birth year 1935. However, in season one, episode five, "How the Tess Was Won", after Al tells Sam that it's 1965, Sam replies that's he was ten in 1965.

Scott Bakula (Sam Beckett), Dean Stockwell (Al Calavicci), Bruce McGill (Weird Ernie and Al the Bartender), and Dennis Wolfberg (Gooshie) are the only actors to appear in the pilot Quantum Leap: Genesis: Part 1 - September 13, 1956 (1989) and the finale Quantum Leap: Mirror Image - August 8, 1953 (1993).

The series traces its roots to Battlestar Galactica (1978), which Donald P. Bellisario co-wrote and co-produced. The series' revival spin-off, Galactica 1980 (1980) was to originally center around time travel, and returning changes in history, back to normal. The concept was dropped after the pilot, but Bellisario stuck with the concept to develop into this show. The concept of Sam inhabiting the identity of another person, to incorporate change for the better, was partly inspired by Heaven Can Wait (1978), which in itself was practically a "word for word" remake of Here Comes Mr. Jordan (1941), with the one exception of changing the lead character from a prize fighter, in Here Comes Mr. Jordan (1941), to a Los Angeles Rams quarterback in Heaven Can Wait (1978).

Throughout the series, Sam Beckett meets many "future" famous people including: Buddy Holly, Michael Jackson, Stephen King, Donald Trump, Marilyn Monroe, Bill Clinton, Dr. Ruth Westheimer, Lee Harvey Oswald, and Elvis Presley.

Sam Beckett and Series Creator Donald P. Bellisario share the same birthday: August 8.

In the first few episodes of the series, Al exited the Imaging Chamber by an unseen door, which opened like a regular door with a turning knob. By the middle of the first season, the effect was changed to the standard rising door with the blue light shining beyond it.

In season two, episode fourteen, "All-Americans", Al Calavicci correctly predicts the Pittsburgh Steelers would be playing in Super Bowl XXX.

This show had several references to Donald P. Bellisario's previous series, Tales of the Gold Monkey (1982), including a character named "Gooshie". Quantum Leap: Ghost Ship - August 13, 1956 (1992) featured Captain Cutter, who was the main character in Tales of the Gold Monkey (1982),

Scott Bakula and Dean Stockwell reunited in Star Trek: Enterprise (2001) season one, episode twenty-one, "Detained".

Sam leaped into nine women or teenage girls: Samantha Stormer in Quantum Leap: What Price Gloria? - October 16, 1961 (1989), Linda Bruckner in Quantum Leap: Another Mother - September 30, 1981 (1990), Darlene Monte in Quantum Leap: Miss Deep South - June 7, 1958 (1990), Billie Jean Crockett in Quantum Leap: 8½ Months - November 15, 1955 (1991), Katie McBain in Quantum Leap: Raped - June 20, 1980 (1991), Cheree in Quantum Leap: A Song for the Soul - April 7, 1963 (1992), Margaret Sanders in Quantum Leap: Liberation - October 16, 1968 (1993), Dr. Ruth Westheimer in Quantum Leap: Dr. Ruth - April 25, 1985 (1993) and Liz Tate in Quantum Leap: Revenge of the Evil Leaper - September 16, 1987 (1993).

In season 5 it was revealed that the very technologically advanced year in the future from which Sam Beckett travels back in time is 1999.

In the first season, the prologues explaining what Quantum Leap was about were done by Scott Bakula as Sam Beckett. By the time season two began, the narrations were done by Deborah Pratt as the voice of Ziggy.

Sam leaped out of the United States seven times: Vietnam in Quantum Leap: The Leap Home: Part 2 (Vietnam) - April 7, 1970 (1990), a plane over the Bermuda Triangle in Quantum Leap: Ghost Ship - August 13, 1956 (1992), Egypt in Quantum Leap: The Curse of Ptah-Hotep - March 2, 1957 (1992), Japan in Quantum Leap: Lee Harvey Oswald - October 5, 1957 - November 22, 1963: Part 1 (1992), the Soviet Union in Quantum Leap: Lee Harvey Oswald - October 5, 1957 - November 22, 1963: Part 2 (1992), a raft in international waters in Quantum Leap: Leaping of the Shrew - September 27, 1956 (1992) and England in Quantum Leap: Blood Moon - March 10, 1975 (1993).

Season one's cliffhanger into season two, was the teaser for "What Price Gloria?" The next season, three other episodes premiered before "What Price Gloria?" aired.

Samuel Beckett was also the name of a famed prolific Irish writer. Some have seen similarities between the series and some of Beckett's work, notably his play Waiting For Godot. However, it is unclear if the naming of the character and/or perceived parallels were intended or coincidental.

Scott Bakula would subsequently star on Star Trek: Enterprise (2001). Several actors and actresses, who appeared on this show, also made appearances on various Star Trek series. Terry Farrell, J.G. Hertzler, and Marc Alaimo appeared on Star Trek: Deep Space Nine (1993), and they also made guest appearances on this show. Robert Duncan McNeill appeared on Star Trek: Voyager (1995) and Quantum Leap: Good Night, Dear Heart - November 9, 1957 (1990). Star Trek: The Next Generation (1987) and Quantum Leap: A Leap for Lisa - June 25, 1957 (1992) had a character named Commander Riker. Carolyn Seymour appeared in Star Trek: Voyager: Persistence of Vision (1995), Star Trek: Voyager: Cathexis (1995), Quantum Leap: A Portrait for Troian - February 7, 1971 (1989), and as Zoey, the evil counterpart to Al, in three episodes of this show.

Malcolm McDowell auditioned for the role of Al Calavicci, which would have made him a time traveler for the second time. The first time was Time After Time (1979). An actor of a similar last name (with a difference of only one letter) but no relation, Roddy McDowall didn't play Al, but was his replacement as a holographic contact in Quantum Leap: A Leap for Lisa - June 25, 1957 (1992).

The run of this show overlapped with the run of the ABC series China Beach. Both programs featured a main character named "Samuel Beckett"--a name that is most associated with the Irish playwright ("Waiting for Godot," "Endgame," "Happy Days") and novelist who is widely considered to be one of the most important writers of the twentieth century.

The show's theme song was revamped for the final season. However, the original version of the theme song was used for airings of that season's episodes in the syndicated versions.

Sam Beckett is revealed to have attended the Massachusetts Institute of Technology, and his friend and guide, Al Calavicci, is mentioned to have also spent some time there.

Al Calavicci drove two different Ferraris in the series: in Quantum Leap: Genesis: Part 1 - September 13, 1956 (1989), he was in a red 1987 Testarossa (which is shown from very low angles so as to keep the identity of the car hidden), and in Quantum Leap: Killin' Time - June 18, 1958 (1992), he is driving a rare 1981 Berlinetta convertible.

Throughout the series, Sam Beckett often encountered implied younger versions of various celebrities, and other figures (Buddy Holly, Woody Allen, Michael Jackson, Stephen King, Sylvester Stallone, Bill Clinton, and others). Writers had proposed scenes for others, but the series was unable to get proper authorization from the people or their estates to depict them.

Sam leaped into four real people: Lee Harvey Oswald in Quantum Leap: Lee Harvey Oswald - October 5, 1957 - November 22, 1963: Part 1 (1992) and Quantum Leap: Lee Harvey Oswald - October 5, 1957 - November 22, 1963: Part 2 (1992), Clint Hill in Quantum Leap: Lee Harvey Oswald - October 5, 1957 - November 22, 1963: Part 2 (1992), Dr. Ruth Westheimer in Quantum Leap: Dr. Ruth - April 25, 1985 (1993), and Elvis Presley in Quantum Leap: Memphis Melody - July 3, 1954 (1993).

In season two, episode ten, "Catch a Falling Star - May 21, 1979", Ernie Sabella played Manny, who in "Man of La Mancha", played Sancho Panza. Many years later, Sabella played the role of Sancho in the Broadway revival of the musical.

Al Calavicci's pilot call sign is "Bingo".

Over the course of the series, Al is seen by people, other than Sam, in nine episodes: by Teresa Bruckner in Quantum Leap: Another Mother - September 30, 1981 (1990), by Maggie Dawson in Quantum Leap: The Leap Home: Part 2 (Vietnam) - April 7, 1970 (1990), by Michael Blake in Quantum Leap: A Little Miracle - December 24, 1962 (1990), by Maria in Quantum Leap: Last Dance Before an Execution - May 12, 1971 (1991), by Tibby Johnson and two other mental patients in Quantum Leap: Shock Theater - October 3, 1954 (1991), by several young children in Quantum Leap: Justice - May 11, 1965 (1991), by Angelita Carmen Guadalupe Cecelia Jimenez in Quantum Leap: It's a Wonderful Leap - May 10, 1958 (1992), by Laura Fuller in Quantum Leap: Trilogy: Part 1 - August 8, 1955 (1992) and by Jessica Elroy in Quantum Leap: A Tale of Two Sweeties - February 25, 1958 (1993).

In season 2, the stolen truck used in the episode Freedom is also the truck used later on in season 2 Maybe, Baby

Sam leaped into ten non-white people: Jesse Tyler in Quantum Leap: The Color of Truth - August 8, 1955 (1989), Eddie Vega in Quantum Leap: All-Americans - November 6, 1962 (1990), George Washakie in Quantum Leap: Freedom - November 22, 1970 (1990), Charlie "Black Magic" Walters in Quantum Leap: Pool Hall Blues - September 4, 1954 (1990), Herbert "Magic" Williams in Quantum Leap: The Leap Home: Part 2 (Vietnam) - April 7, 1970 (1990), Ray Harper in Quantum Leap: Black on White on Fire - August 11, 1965 (1990), Jesus Ortega in Quantum Leap: Last Dance Before an Execution - May 12, 1971 (1991), Cheree in Quantum Leap: A Song for the Soul - April 7, 1963 (1992), Roberto Gutierrez in Quantum Leap: Roberto! - January 27, 1982 (1992) and Nikos Stathatos in Quantum Leap: Leaping of the Shrew - September 27, 1956 (1992),

Inspired the song "I Always Feel Like I'm Gonna Quantum Leap" by Bonecage.

Donald P. Bellisario and Scott Bakula have both expressed their ire with NBC over the series finale. Originally, Bellisario was asked to write an episode that could function either as a season finale cliffhanger, or as an end to the series. When Bellisario complied, the cast and crew were assured of the series renewal. In the eleventh hour, NBC decided to cancel the series after all, and re-edited the ending, with title cards revealing the fate of Sam and Al. This was one of at least four endings, at least two of which were filmed. If the series was to end, Bellisario originally planned to have Al and Beth as an old married couple, discussing how they would locate Sam, who had leapt again. Had the series continued, Bellisario planned to have Sam leap into a space station in the distant future, and Al becoming a leaper himself to rescue Sam.