The Simpsons is the Trope Namer for the Couch Gag trope, where the original opening sequence had several couch gags. Sometimes they just skip straight to the driveway and do the couch gag, or some other abridged opening:
Lisa plays a different solo on her saxophone. Since the show's switch to High Definition, some episodes have featured Lisa playing another instrument such as a trumpet or violin instead.
The literal 'couch gag', the family gathering on the couch in a (usually) humorous animation. (This is also the only gag that's never cut in syndication, though many of the first episodes to be syndicated saw their original couch gags get replaced with the one where the Simpsons find an identical family already sitting on the couch.)
The HDTV opening introduced in season 20 introduced five additional couch gags:
Something different flies in front of the Simpsons logo (but it's usually a three-eyed crow).
When the head of the Jebediah Springfield statue falls on Ralph's head, he will usually make a muttering noise, but sometimes he will actually say something, such as "I see stars!" or "It's dark!"
Early on, when Bart ran over him, Barney would also sometimes exclaim something (such as "BART!") instead of belching.
A billboard across the street from Springfield Elementary advertises something different each episode.
The Simpsons' wall-mounted HDTV falls off the wall in some episodes, and does not in others.
Other gags are used occasionally during the ending credits:
The Gracie Films Vanity Plate at the end of the episode sometimes undergoes a Logo Joke where it has different sound effects playing besides just the "shh" and the little jingle that plays.
The most regular appearing one is a shriek and minor-key organ variation of the jingle which follows some of the Halloween episodes.
A gunshot is inserted here for "Who Shot Mr. Burns? Part 1."
Another has Grandpa Simpson saying "Oh, sorry."
The fourth clip show has Snake cursing the "Gracie music dude."
The song or sound played during the credits may vary based on the theme of the preceding episode:
Throughout the credits of "Bart Star," Homer, drunk with power from being made Head Coach of the pee-wee football team, 'cuts' several people when their names appear,note This is to say, everyone listed in the end credits except guest star Joe Namath. and when the woman does her shush he said "You're cut too, Shushy!"
Sometimes the closing theme is rendered in a different musical motif based on the theme of the episode (such as an ice rink organ after a hockey-themed one), or an instrumental performed by a 'special musical guest' (past bands to interpret the theme during the end credits include NRBQ, Sonic Youth, Brave Combo, Fall Out Boy and Yo La Tengo).
The Halloween specials also generally feature gags within the credits, with puns on the names in the credits ("Matt Groaning" or "Bat Groening" being almost inevitably featured).
For some episodes, the entire opening is changed:
When the show was first put into syndication in 1994, many episodes from Seasons 1 to 5 used the couch gag from "Rosebud" (where the Simpsons find duplicates of themselves already on the couch). All episodes afterward usually retained their original couch gags.
On the original airing of "Springfield Up", the opening sequence is cut (among other edits) in order to fill up time for the premiere of a new trailer for The Simpsons Movie. Subsequent airings use the couch gag from "Ice Cream of Margie (with the Light Blue Hair)" (wherein the family are depicted as cockroaches).
For the episode "He Loves to Fly and He D'ohs", the first episode of the regular TV series following the release of The Simpsons Movie, almost every element of the opening was changed to reflect events of the movie such as Springfield in ruin, the silo still lashed to the top of Homer's car, and Spider-Pig/Harry Plopper waiting for them on the couch.
For the episode "To Surveil with Love", the opening credits were completely replaced by an animated music video set to "TiK Tok", though the gathering-on-the-couch gag still appears at the end.
A live-action version of the sequence, originally made as a promo on British TV network Sky1 (which, perhaps not coincidentally, was also a NewsCorp property), was eventually used as an actual show opening on the season 17 episode "Homer Simpson, This Is Your Wife".
If an episode is too short, a very long couch gag will start to play to fill time. Three noticeable examples include one where the family performs a chorus line while the living room turns into a circus,note This one was used more than any other as a way of filling time, with a total of eight uses — and it still couldn't fill enough broadcast time when "Cape Feare" aired, hence the famous half-minute of Sideshow Bob constantly stepping on rakes. one where the camera zooms out of their house and into outer space and keeps going until it zooms out of Homer's head again, and one where Homer is seen evolving from a single-celled organism.
Sometimes the writers enjoy meta-humor about the blackboard gags.
In the episode "Skinner's Sense of Snow", Bart complains that he's written on the board so often that his wrist sounds like a cement mixer (and rotates his wrist to prove his point).
For "Thirty Minutes over Tokyo", the 10th-season finale, Bart writes "I'm so very tired."
For "Simpsons Tall Tales", the 12th-season finale, Bart writes "I should not be twenty-one by now," which he would be if he had been played by an actual ten-year-old boy when the series began.
For "The Parent Rap", Bart writes "Nobody reads these anymore."
For "Bonfire of the Manatees", Bart writes "Does any kid still do this anymore?", as a reference to how Writing Lines has gradually become a Discredited Trope.
For "Sweet Seymour Skinner's Baadaaaass Song," the 100th episode, heavily advertised by Fox, Bart writes "I will not celebrate meaningless milestones."note It isn't the hundredth episode in production order, however; that honor goes to "Lisa's Rival," which aired in season 6. Neither "Lisa's Rival" nor "Sweet Seymour Skinner's Baadaaaass Song" make a big deal in-universe, during the contents of their episode, about hitting the century mark.
In the opening for "Homer the Heretic," Bart writes "I will not defame New Orleans." The previous episode, "A Streetcar Named Marge," had featured a song about how horrible New Orleans was, in a spoof of the song from the musical Sweeney Todd: The Demon Barber of Fleet Street. Bart's writing on the board was intended as an apology to those who were offended.
Similarly, "Homer Scissorhands" had a guest star whose name was misspelled in the credits; the following episode, "500 Keys," had Bart writing the correct spelling on the blackboard over and over.
"Half-Decent Proposal" had "I will not bite the hand that feeds me Butterfingers." Marge's crusade against refined sugar in "Sweets and Sour Marge," just two episodes earlier, sees Chief Wiggum disposing of the town's supply of Butterfingers in a fire, only for the fire to reject them. "Not even the fire wants them," comments Wiggum. This was an inside joke about the show's long history of Simpsons characters (particularly Bart) appearing in Butterfinger ads. This was written around the time the contract with Butterfinger ended; needless to say, the company did not offer to renew the contract.
When Matt Groening announced that Springfield, Oregon was the inspiration for Springfield, that week's episode ("Beware My Cheating Bart") opened with the words "Now entering Oregon" next to the main title, while the chalkboard gag read "The true location of Springfield is in any state but yours."
In "Take My Life, Please," the first HD episode, Bart writes "HDTV is worth every cent."
In "Barting Over," we see Bart writing "I will not ..." and then abruptly stopping before destroying the chalkboard with an axe.
The 500th episode, "At Long Last Leave," featured Milhouse writing "Bart's earned a day off" on the chalkboard while Bart smugly looked on.
"Black-Eyed, Please" has Bart writing on a whiteboard in marker, the phrase being "Sorry I broke the blackboard."
In "Four Regrettings and a Funeral", as a tribute to the late Marcia Wallace, Bart writes "We'll really miss you, Mrs. K." with a sad look on his face. Grab the hankies.
In "Married to the Blob", Bart writes "Judas Priest is not death metal" on the chalkboard, a reference to the numerous Internet complaints about that description of the band as such in the previous episode, "Steal This Episode".
In "Trash of the Titans", where the eponymous Couch Gag would be, Homer, Marge, Lisa and Maggie end up running into Bart's classroom, where they find Bart writing, "I will not mess with the opening credits." (A similar gag was present in "MyPods and Boomsticks", except there, the setting was the living room, and Bart was writing, "I will not bring the chalkboard home.")
In the Tonight Someone Dies episode "Clown in the Dumps", Bart writes "Spoiler alert: Unfortunately, my dad doesn't die."
In the 25th-season premiere "Homerland", Bart writes, "25 years and they can't come up with a new punishment?"
Other Couch Gags of Note
This could take a while ... maybe enough for a chorus line!
Recent episodes now have had gags done by guest animators:
Many chalkboard gags satirize current or meta-related events in real life:
"Two Cars in Every Garage and Three Eyes on Every Fish": "It's potato, not potatoe."note Only used on a repeat airing on June 25, 1992, making fun of Dan Quayle's infamous 'potatoe' blunder.
"Dead Putting Society": "I am not a 32-year-old woman."note Nancy Cartwright was 32 at the time.
"Homer the Heretic": "I will not defame New Orleans."note See above.
"Homer's Barbershop Quartet": "I will never win an Emmy."note This episode was the first after the 1992–93 Emmy nominations were announced and was the first time the show was eligible to be nominated for the award for Outstanding Comedy Series (which didn't happen). For the record, Seinfeld won the award that year, and only twice has the Academy of TV Arts and Sciences nominated a primetime cartoon for Outstanding Comedy: The Flintstones in 1961 and Family Guy in 2009 (they lost, respectively, to The Jack Benny Program and 30 Rock).
"Secrets of a Successful Marriage": "Five days is not too long to wait for a gun."note The U.S. government had recently passed the highly controversial Brady Handgun Violence Prevention Act, which required firearm buyers to hand over their money and wait five business days before they could receive their gun.
"The Trouble with Trillions": "I will not demand what I'm worth."note The show's voice cast was in a heated argument with Fox executives over pay disputes.
"Natural Born Kissers": "I was not the inspiration for 'Kramer'."note This episode aired three days after Seinfeld's series finale.
"D'oh-in' in the Wind": "No one cares what my definition of 'is' is."note This refers to Bill Clinton's mush-quoted statement to the grand jury during the Lewinsky trial.
"Mayored to the Mob": "'The President did it' is not an excuse."note This episode was the first aired after President Clinton's impeachment.
"Sunday, Cruddy Sunday": "I will not do the Dirty Bird."note The Dirty Bird was a victory dance done by the Atlanta Falcons during Super Bowl XXXIII.
"Little Big Mom": "I will not create art from dung."note A reference to the controversial "The Holy Virgin Mary" painting in New York City, which was a painting of the Virgin Mary created with elephant dung.
"A Tale of Two Springfields": "I will not plant subliminal messagores."note During the 2000 presidential election, Republican ads were being ran that highlighted the word 'rat' in 'Democrats.'
"Lisa the Tree Hugger": "I am not the acting President."note The 2000 presidential election winner had not yet been decided.
"New Kids on the Blecch": "I will not buy a Presidential pardon."note At the time this aired, it had recently come to light that in his last two days in office, Bill Clinton issued many presidential pardons, mostly to people who'd supported him.
"Bye Bye Nerdie": "I will not scare the Vice President."note Dick Cheney was in the hospital with a heart condition.
"She of Little Faith": "I do not have a cereal named after me."note At that time, Bart Simpson Peanut Butter Chocolate Crunch was being sold.
"Half-Decent Proposal": "I will not bite the hand that feeds me Butterfingers."note See above
"The Sweetest Apu": "I will never lie about being cancelled again."note A reference to a Flip Flop of God moment by Matt Groening about the fate of the series, at which his British interviewer freaked out.
"Homer of Seville": "The Wall Street Journal is better than ever."note Rupert Murdoch had recently bought it.
"The Squirt and the Whale": "South Park—we'd stand beside you if we weren't so scared."note The South Park episode "201" was heavily censored because of death threats from a Muslim extremist group, which led many to accuse Comedy Central of being cowards. Reruns have changed the joke to "Je ne suis pas français" ("I am not French" — itself a reference to the punitive line "Je ne parle pas français" in "Girls Just Want to Have Sums").
"500 Keys": "It's Kristen Schaal, not Kristen Schall."note A reference to a spelling mistake in the credits in "Homer Scissorhands."
"Replaceable You": "It's November 6th—how come we're not airing a Halloween show?"note That year's Treehouse of Horror episode seemed like the first to air in October for about a decade. As a matter of fact, that year's Treehouse of Horror (the 22nd) was the second in three years to air in October; the 20th Treehouse of Horror aired on October 18, 2009, and was the first to air in October in a full decade (the 10th aired on October 31, 1999).
"Homer Goes to Prep School": "I will obey Oscar® campaign rules from now on."note The Simpsons theatrical short The Longest Daycare had been nominated for the Academy Award for Best Short Film; it lost to Paperman.
"Love Is a Many-Splintered Thing": "I was not nominated for 'Best Spoken Swear Word'."note This aired the night of the 2013 Grammy Awards.
"Four Regrettings and a Funeral": "We'll really miss you Mrs. K."note A tribute to Marcia Wallace, the longtime voice of Edna Krabappel. To emphasize the more serious nature of the message, the sentence is written only one time on the chalkboard and Bart has a more solemn facial expression.
"Married to the Blob": "Judas Priest is not death metal."note A reference to fan complaints about a joke in "Steal This Episode" where they were described as such. Reruns have changed the joke to "If you haven't broken your Christmas presents yet, you're not trying."