Jean was offered a job as a writer on the animated sitcom The Simpsons in 1989, alongside Reiss, and together they became the first members of the show's original writing staff.

In 1994, Jean and Reiss signed a three-year development deal with The Walt Disney Company to produce other television shows for ABC.

Among multiple pitches made by the duo, their sole project with ABC to come to fruition was the live-action sitcom Teen Angel, which was cancelled in its first season.

[2] Jean was also one of the writers and producers who worked on The Simpsons Movie, a feature-length film based on the series, released in 2007.

[6] After working at his father's hardware store,[7] Jean arrived at Harvard University when he was sixteen years old and graduated in 1981[8] with a bachelor's degree in mathematics.

[9] Daryl Libow, one of Jean's freshman roommates, said he was a "math whiz" when he arrived at Harvard but "soon blossomed and found his comedic feet.

[3][13] In 1989, Jean was offered a job as a writer on the animated sitcom The Simpsons,[14] a show created by Matt Groening, James L. Brooks and Sam Simon that continues to air today.

[13] While watching the first episode of the show, "Simpsons Roasting on an Open Fire", premiering on television in December 1989, Jean opined to himself that the series was the greatest project he had been involved with and desired to continue working on it for the rest of his professional career.

[6] What he enjoyed most about The Simpsons at the time was something he recognized from Brooks' previous work: although the show was largely based on humor, it had depth and warmth.

[16] A showrunner has the ultimate responsibility of all the processes that an episode goes through before completion, including the writing, the animation, the voice acting and the music.

"[16] The first episode Jean and Reiss ran was "Mr. Lisa Goes to Washington" (aired September 26, 1991), and they felt pressured to make it good, so much so that they did six to seven rewrites of the script in order to improve its humor.

"[10] Comedy writer Jay Kogen has said that "those years with Al Jean and Mike Reiss running it were pretty darn good.

[27] In 1994, Jean and Reiss signed a three-year deal with The Walt Disney Company to produce other television shows for ABC.

"[28] The pair periodically returned to work on The Simpsons— for example, while under contract at Disney they were allowed to write and produce four episodes of the show, including season eight's "Simpsoncalifragilisticexpiala(Annoyed Grunt)cious" (1997).

[29] "What has defined the Al Jean era is the show's definitive move into the mainstream of American TV and culture.

By now The Simpsons is the most successful show in the history of television—it's a long way from the young, mouthy, experimental series on the upstart network [Fox].

Following Scully's departure in 2001, Jean returned to the showrunner position with the start of the thirteenth season (2001–2002),[17] likewise without Reiss.

[34] The Simpsons producers were initially worried that creating a film would have a negative effect on the show, as they did not have enough crew to focus their attention on both projects.

He told IGN that he enjoys doing them because he has not seen some of the episodes in ten to fifteen years, and "it's kind of like a reunion to see some of the people that I worked with before, so it's a really pleasant experience.

[3][13] In 1997, he and Reiss won an Annie Award in the "Best Producing in a TV Production" category for the Simpsons episode "The Springfield Files".

[38] In 1991 they shared the Writing A Comedy Series CableAce Award for the It's Garry Shandling's Show Episode "My Mother The Wife".