The show includes a vast array of quirky supporting characters, which include Homer's friends Barney Gumble, Lenny Leonard, and Carl Carlson; the school principal Seymour Skinner and staff members such as Edna Krabappel and Groundskeeper Willie; students such as Milhouse Van Houten, Nelson Muntz, and Ralph Wiggum; shopkeepers such as Apu Nahasapeemapetilon, Comic Book Guy, and Moe Szyslak; government figures Mayor "Diamond" Joe Quimby and Clancy Wiggum; next-door neighbor Ned Flanders; local celebrities such as Krusty the Clown and news reporter Kent Brockman; nuclear tycoon Montgomery Burns and his devoted assistant Waylon Smithers; and many more.

The latter point introduces another snag in the floating timeline: historical periods that are a core part of a character's backstory remain so even when their age makes it unlikely or impossible, such as Grampa Simpson and Principal Skinner's respective service in World War II and Vietnam.

[18] Most episodes end with the status quo being restored, though occasionally major changes will stick, such as Lisa's conversions to vegetarianism and Buddhism, the divorce of Milhouse van Houten's parents, and the marriage and subsequent parenthood of Apu and Manjula.

[30] The colorist, "Georgie" Gyorgyi Kovacs Peluce (Kovács Györgyike)[31][32][33][34][35][36] made the characters yellow; as Bart, Lisa, and Maggie have no hairlines, she felt they would look strange if they were flesh-colored.

[42] List of showrunners throughout the series' run: Matt Groening and James L. Brooks have served as executive producers during the show's entire history, and also function as creative consultants.

[30] The first team of writers, assembled by Sam Simon, consisted of John Swartzwelder, Jon Vitti, George Meyer, Jeff Martin, Al Jean, Mike Reiss, Jay Kogen, and Wallace Wolodarsky.

Group rewriting sessions develop final scripts by adding or removing jokes, inserting scenes, and calling for re-readings of lines by the show's vocal performers.

[57][58] The Simpsons has six main cast members: Dan Castellaneta, Julie Kavner, Nancy Cartwright, Yeardley Smith, Hank Azaria, and Harry Shearer.

The show's revenue continued to rise through syndication and DVD sales, and in April 2004 the main cast stopped appearing for script readings, demanding they be paid $360,000 per episode.

[74] In 2008, production for the twentieth season was put on hold due to new contract negotiations with the voice actors, who wanted a "healthy bump" in salary to an amount close to $500,000 per episode.

Repeat "special guest" cast members include Albert Brooks, Phil Hartman, Jon Lovitz, Joe Mantegna, Maurice LaMarche, and Kelsey Grammer.

[128] Other examples purported as The Simpsons predicting the future include the introduction of the smartwatch, video chat services, Richard Branson's spaceflight[129][130] and Lady Gaga's acrobatic performance at the Super Bowl LI halftime show.

[137][138] Mark Liberman, director of the Linguistic Data Consortium, remarked, "The Simpsons has apparently taken over from Shakespeare and the Bible as our culture's greatest source of idioms, catchphrases and sundry other textual allusions.

[140] Groundskeeper Willie's description of the French as "cheese-eating surrender monkeys" was used by National Review columnist Jonah Goldberg in 2003, after France's opposition to the proposed invasion of Iraq.

The Simpsons changed this perception,[28] initially leading to a short period where networks attempted to recreate prime-time cartoon success with shows like Capitol Critters, Fish Police, and Family Dog, which were expensive and unsuccessful.

[226] On October 21, 2014, a digital service courtesy of the FXNOW app, called Simpsons World, launched with every episode of the series accessible to authenticated FX subscribers, and is available on game consoles such as Xbox One, streaming devices such as Roku and Apple TV, and online via web browser.

[261] In 2004, The Simpsons replaced The Adventures of Ozzie and Harriet (1952 to 1966) as the longest-running sitcom (animated or live action) in the United States in terms of the number of years airing.

[289] In 2010, Entertainment Weekly named Homer "the greatest character of the last 20 years",[290] while in 2013 the Writers Guild of America listed The Simpsons as the 11th "best written" series in television history.

[298] Bart's rebellious, bad boy nature, which underlies his misbehavior and rarely leads to any punishment, led some people to characterize him as a poor role model for children.

"[304][305] The show also received criticism from the nuclear power industry in its early years, with its portrayal of the evil boss Mr. Burns and "bungling idiot" employees (including Homer Simpson himself) with their lack of safety and security.

[307] In the latter case, Rio de Janeiro's tourist board—which claimed that the city was portrayed as having rampant street crime, kidnappings, slums, and monkey and rat infestations—went so far as to threaten Fox with legal action.

[316][317][318] Jim Schembri of The Sydney Morning Herald attributed the decline in quality to an abandonment of character-driven storylines in favor of celebrity cameo appearances and references to popular culture.

"[319] In 2010, the BBC noted "the common consensus is that The Simpsons' golden era ended after season nine",[320] and Todd Leopold of CNN, in an article looking at its perceived decline, stated "for many fans ... the glory days are long past.

[322] Jon Heacock of LucidWorks stated that "for the first ten years [seasons], the show was consistently at the top of its game", with "so many moments, quotations, and references – both epic and obscure – that helped turn the Simpson family into the cultural icons that they remain to this day".

[328] John Ortved, author of The Simpsons: An Uncensored, Unauthorized History, characterized the Jean era as "toothless",[329] and criticized what he perceived as the show's increase in social and political commentary.

[336] Alan Sepinwall and Matt Zoller Seitz argued in their 2016 book titled TV (The Book) that the peak of The Simpsons are "roughly seasons 3–12", and that despite the decline, episodes from the later seasons such as "Eternal Moonshine of the Simpson Mind" and "Holidays of Future Passed" could be considered on par with the earlier classic episodes, further stating that "even if you want to call the show today a thin shadow of its former self, think about how mind-boggingly great its former self had to be for so-diminished a version to be watchable at all.

The criticisms were referenced in the season 29 episode "No Good Read Goes Unpunished", when Lisa breaks the fourth wall and addresses the audience by saying, "Something that started decades ago and was applauded and inoffensive is now politically incorrect.

[347] On June 26, 2020, in light of the various Black Lives Matter protests, Fox announced that recurring characters of color (Carl Carlson and Dr. Hibbert, among others) would no longer be voiced by white actors.

[353] The book was a success and due to this, Groening and his companions Bill Morrison, Mike Rote, and Steve and Cindy Vance created the publishing company Bongo Comics.

[392] On April 9, 2009, the United States Postal Service unveiled a series of five 44-cent stamps featuring Homer, Marge, Bart, Lisa and Maggie, to commemorate the show's twentieth anniversary.