A ChristmasEpisode of the show (and what would have been the final episode of the entire series) where the viewers see life for The Simpsons in 2041: Bart is a deadbeat divorced dad living in an apartment complex that used to be the elementary school, Lisa (after a string of straight and lesbian relationships in college) marries Milhouse and has a rebellious teen daughter named Zia, and Maggie is a pop singer (despite that we still never hear her talk) with a baby on the way.
!!''Holidays of Future Passed'' has the following tropes:

* AbusiveParents: Thankfully averted with Bart and Lisa who, despite having problems with their kids, don't do what Homer and Marge did in terms of parenting -- mostly because they're better than that, and mostly because Homer's strangling of Bart became such a problem that a law was made to forbid child abuse (particularly strangling of any child) once and for all (called "Homer's Law").
* AbsurdlyYouthfulMother: Lisa doesn't look much older than her teenage daughter.
* AwayInAManger: Slightly parodied with Kearney as Joseph and helping Maggie (both the Mary expy as well as the "star") to the hospital and her having to be taken to the Manger...Wing.
* BabiesEverAfter: All the Simpsons kids have their own kids and Maggie having first daughter. [[SubvertedTrope The "ever after" would have been true had the show ended at that point, but it's not]].
* BaitAndSwitch: Aside from the FoodPills parody, there's also a cab driver (Kearney) who drove Maggie to the hospital. When his cab's computer took his order to drive to the hospital ("Computer, hospital") as an order to go to the [[ExactWords computer hospital]], he said he'd have to do it the old-fashioned way. He took a pair of gloves and ordered them to drive to the hospital.
* BookEnds: The first ''Simpsons'' episode was a Christmas episode ("Simpsons Roasting Over an Open Fire"). If this actually aired as the series finale, it would have ended with a Christmas episode.
* CallBack: Bart is shown to have married (and divorced) Jenda from "Future-Drama".
** Homer accidentally getting Edna killed echoes what happened to Maude, though, unlike Maude, we don't see how Homer had a hand in killing Edna.
** HarsherInHindsight: A year after this episode aired, Edna's voice actor, Marcia Wallace, passed away, and her character, Edna Krabappel, will never be seen again.
* ChalkOutline: Several of them at Moe's. One of them was implied to be of Sideshow Bob.
* CloningBlues: Ralph is revealed to have made clones of himself...who get killed with alarming frequency.
* DrowningMySorrows: Bart and Lisa do this in the treehouse after Zia won't spend time with Lisa and after Bart's sons prefer spending time with Homer then with him.
* ExperimentedInCollege: Lisa has several girlfriends in college (and at one point, two girlfriends at once), and then gets engaged to Milhouse soon after graduating.
* FamousFamousFictional: A variation in this exchange:
-->'''Lisa:''' My daughter thinks I'm some sort of dictator, like Hitler or Prince Harry.\\
'''Homer:''' Ah, Bloody Harry. He brought back beheading in a big way.
* FoodPills[=\=]InstantMassJustAddWater: Parodied. When Marge wants to make a cake, she takes out a tablet and adds water. The tablet turns into... a recipe card, which she uses to make a cake with real ingredients.
* FreakyFridayFlip: Carl and Lenny are revealed to have swapped brains in the future. One of them has an ex-wife who swapped brains with a monkey.
* GenerationXerox: Bart's kids have a strained relationship with their dad, but get along fine with their grandfather. Homer points out that this is par for the course with every son.
** Lisa tries to understand a daughter that seems very different from her and can be condescending at the drop of a hat.
--->'''Lisa:''' You have no idea what that's like.\\
'''Marge:''' [[DeadpanSnarker Uh-huh.]]
** Maggie's daughter sucking on a pacifier.
** Apu and Manjula's Octuplets work at the Kwik-E-Mart with their dad. They also each have their own set of octuplets.
* HotMom: Lisa. By the end of the episode, Maggie's one as well.
* HumanPopsicle: Along with Grandpa, other Simpson regulars are cryogenically frozen.
* NeuralImplanting
* NoodleIncident: Lenny and Carl switched brains so Lenny could get back together with his wife, who was sleeping with Carl.
-->'''Carl:''' Turns out she had switched brains with a monkey on a Japanese game show, and it just got weirder from there.\\
'''Lenny:''' Ah, I found it quite normal.
** Homer somehow got Edna killed.
* NotSoDifferent: Bart and Lisa bond in the treehouse over some beer and their parenting difficulties.
* TheNothingAfterDeath: Maude's ghost claims as such to Ned, though he doesn't seem to notice.
* OlderThanTheyLook: Lisa is almost 40 in the episode. She looks 10-15 years younger. Boy, did she age well.
* ProductPlacement: Google
* {{Reincarnation}}: Apu thinks his brother was reincarnated as a cow, but it insists it's just an animal that died 600 years ago.
* SeriesFauxnale: This episode was conceived as a DistantFinale in case the show really was going to end.
* ShoutOut: In the montage, Bart and Lisa dress up as [[ComicBook/VForVendetta Guy Fawkes]] and Franchise/SailorMoon (or a ''Sailor Moon''-inspired magic girl superhero) respectively during their teen years.
** Selma's [[{{Sexbot}} lovebot]] looks like Gigolo Joe (Jude Law's character) from ''[[Film/AIArtificialIntelligence AI: Artificial Intelligence]]''.
* SubwaysSuck: In the future, the interior of planes look and sound like subways and teleportation is the transportation of choice for the poor, the elderly, and pregnant women.
* TalkingToHimself: Nancy Cartwright voices Bart's sons.
** Likewise Yeardley Smith (who doesn't voice anyone else except for Lisa [and, on rare occasions, girls who look or act like Lisa, like Lisabella from "The Last Tap Dance in Springfield" or the Pacific Islander girl Homer names "Lisa, Jr." on "Missionary Impossible"]) voices Zia.
* TimeSkip: Unlike previous episodes that take place in the future, there's no framing device here. The only present day scene is the one in the beginning with the family photo.
* TooDumbToLive: Ralph Wiggum's clones.
* TookALevelInKindness: Homer by the time he's a grandparent, he's a really good grandfather and has learnt from his mistakes.
* UncannyFamilyResemblance: Per usual, the next generation of Simpson kids greatly resemble their parents.
* VictoriousChildhoodFriend: Milhouse manages to marry Lisa
* TheVoiceless: Maggie, in continuing with the RunningGag that was set up on "Lisa's Wedding."
* WhatCouldHaveBeen: As mentioned in SeriesFauxnale, this episode was slated to be the final episode, as FOX was having budget issues with the show (the show was becoming too expensive to advertise and ''Bob's Burgers'' was becoming more popular, blowing both this show and most of SethMacFarlane's shows out of the water). Once everyone agreed to take a pay cut in order to keep the show afloat for at least two more seasons (the 24th season and the current 25th season. On October 4, 2013, it was announced that ''The Simpsons'' would have a ''26th'' season, and Al Jean has said he wanted the show to end after 30 seasons), this was set as a Christmas episode.
* YourCheatingHeart: Implied.
-->'''Bart:''' Nelson still calls you?\\
'''Lisa:''' Let's just say someone calls someone.