Originally aired on December 14, 2003.

When Carl gives Homer a DVD player and the first season of ''Series/MagnumPI'', Homer forgets that he is Lenny’s “Secret Santa”, so he hastily gives him Certs. Also, Mr. Burns gives everyone a caferteria voucher as a Christmas bonus, except Homer, who gets a Joe [=DiMaggio=] baseball card (which, him being Burns, believes is worthless - Burns is so outdated he thinks [=DiMaggio=] is a rookie and Homer's surprise was about the fact they "started" to allow ethnics in the big leagues)). Homer trades it in to Comic Book Guy, who gives him everything in his register. With this small fortune, the Simpsons go Christmas shopping and Homer promoses to spend his money on a huge Christmas tree, but instead squanders it on a personalized talking astrolabe. When his family finds out, they call him out on his selfish act, with Marge saying that he doesn't care about anybody but himself. What’s worse is that Homer can’t return the astrolabe as the astrolabe itself reminded him after Homer was called out for his selfishness.

Later that night, Homer watches ''Mr. [=McGrew=]’s Christmas Carol'' and sees the Scrooge-type character doomed to go to Hell because of his selfishness. Fearing the same might happen to him, Homer decides to change his ways and become the nicest person in town. Around town, Homer performs good deeds for Springfield’s citizens, including giving his old clothes to charity, giving Lenny a photo cube, giving Marge the last pork chop at dinner and building a skating rink in his backyard. This kind attitude of Homer’s causes resident nice guy Ned Flanders to get jealous and so he competes buy dressing up as Santa and giving everyone in town a free gift and renting his house to a fraternity. Homer decides to get back by buying everyone a new car, but Lisa tells him that as a Buddhist, she believes there’s too much commercialism in Christmas and that everyone is better off without presents.

Inspired, Homer decides to to the “ultimate good deed” by stealing Christmas. That morning, as Homer prepares to burn the stolen gifts in a bonfire, an angry mob shows up. But Homer manages to calm everyone down by showing them a Christmas star in the sky (actually a flare from Hans Moleman). Homer gives back the gifts and everyone joins in singing a Christmas carol, including Moe after once again attempting suicide.

!!"'Tis the Fifteenth Season" contains examples of:

* ActuallyPrettyFunny: Marge commented the ''Series/StarTrekTheOriginalSeries'' version of ''Literature/AChristmasCarol'' looked good.
* TheAntiGrinch: Homer decides to change his ways and become the nicest person in town. When he gets told there's too much commercialism in Christmas and that everyone is better off without presents, Homer decides to to the "ultimate good deed" by stealing Christmas. Needless to say, this doesn't work.
* ArtShift: The ShowWithinAShow Christmas specials "Christmas with the California Prunes" ("This is offensive to Christians and prunes.") and "The Year Santa Got Lost" ("Jimmy Stewart as a puppet is just wrong.") are animated via claymation.
* BaitAndSwitch: Snake has this to say after being robbed by Homer: "Ho, I've been robbed! Man, so this is how it feels. I'd better see my shrink... and rob his ass."
* BigFatFuture: In the ''Series/StarTrekTheOriginalSeries'' version of ''Literature/AChristmasCarol'', the Ghost of Christmas Yet To Come attacks the Enterprise with visions of the future. Scotty is horrified by how fat he's going to become.
* BigNo: Three in the same scene. [=McGrew=] does one on the TV when his name appears on the gravestone, Homer does one when he imagines his name appearing on it, then he does another one when he reads it correctly (""Unloved by ''all''"?! NO!").
* BlatantLies: When the Astrolabe makes a comment within earshot of the family, exposing Homer, Marge asks what that was, and Homer responds with, "Woohoo! [[TheQuietOne Maggie]]'s talking!"
* CallingTheOldManOut: When the family find out Homer blew their money on the Astrolabe, he tries to say that if he's happy, he's "less abusive" to them. Lisa shoots him down with one sentence, without even needing to raise her voice: "No, Dad. This time, you were just plain selfish."
* ContinuityNod: Lisa reminds Homer that she's a Buddhist after converting in "She of Little Faith".
* DisappearedDad: Nelson's missing father is referred to again in this episode.
* DrivenToSuicide: Moe, as per every Christmas, attempts and fails to commit suicide at the end.
* EvenEvilHasStandards: Even Mr. Burns gives a more thoughtful gift than Homer.
* ExiledToTheCouch: Homer sleeps on the couch at night after angering his family with his selfishness.
* EyeScream: Homer gives Lenny a photo cube with the edges trimmed so Lenny won't jab the points in his eye.
-->'''Lenny:''' Now it only hurts a little.
* ForWantOfANail: Essentially most of the plot happens because Mr Burns gave Homer a Joe [=DiMaggio=] baseball card.
* HowTheCharacterStoleChristmas
-->'''Homer''': You're a hero, Homer J.,\\
You're as crafty as a skunk.\\
You'll make everybody happy when they're rid of Flanders' junk,\\
Homer Ja-a-ay.\\
I'd call you a double bacon genius-burger,\\
And just a little drunk!
* HeelRealization: Homer watching a Christmas special on TV makes him decide to be a better person.
* {{Hypocrite}}: Lisa tells Homer about how she feels that Christmas would be better without all the materialism and commercialism. She is later shown among the mob wanting to kill Homer for taking their stuff. Although it's just as likely she's upset that Homer took her advice to mean he should rob everyone in town.
* InelegantBlubbering: After Homer decides to be nicer, he lets Marge have the last pork chop at dinner. Marge, who apparently has waited years for Homer to offer that, starts crying tears of joy and eats the chop with her bare hands. While she's doing this Marge gushes over how good Homer's thoughtfulness tastes. Homer, and the kids, are understandably creeped out by Marge's blubbering.
** Homer himself also does this when the Personalized Talking Astrolabe tells him it can't be returned.
* InstantSedation: While Homer is stealing Christmas, he is spotted by one of Apu and Manjula's octopulets (a la Cindy Lou Who), so he knocks her (and a teddy bear) out with a chloroform rag.
* ItsAllAboutMe: Homer before he decides to be a better person. He forgets he's Lenny's secret Santa, annoying both him and Carl. Carl in particular calls Homer the most selfish man he knows. Homer says that Mr Burns is more selfish than him, leading straight into the RightBehindMe example below. Then, he buys ''keyrings'' for his family's presents and spends almost everything else on the Personalized Talking Astrolabe, meaning the only Christmas tree they can afford is so dry bursts into flames when Homer rubs it. Obviously, Marge and the kids are ''not'' happy when they find out.
* LimitedWardrobe: Homer is shown donating his old clothes to the needy. Cut to hobos wearing white shirts and blue pants.
* LoopholeAbuse: The Springfield Heights Promenade has the following slogan: "Our prices discriminate because we can't"
* NiceGuy: Homer tries very hard to be one of these after his HeelRealization. He does this by donating his old clothes to hobos, giving Lenny a photo cube to make up for being a bad secret Santa to him earlier in the episode, offers Marge the last pork chop (causing her to break down in [[InelegantBlubbering tears of joy]]), orders Burns to donate to the church collection plate, and builds an ice rink in the back yard. Marge is very happy by Homer's newfound unselfishness, and Gil even calls him "the nicest man in town", right in front of Ned Flanders.
* RealityEnsues: Breaking and entering into houses to steal stuff (in this particular case, Christmas presents) equals a pissed-off lynch mob armed with TorchesAndPitchforks, ''not'' people deciding to learn the True Meaning Of Christmas. Homer got ''very'' close to buying it as a result.
* RightBehindMe: To give an example of somebody more selfish than him, Homer started describing Mr. Burns, who overheard him. [[SubvertedTrope Fortunately]], Burns thought Homer was talking of a woman named Kathy, who ''does'' look like Burns except for the fact she's a woman.
* ShoutOut:
** Homer watches ''[[WesternAnimation/MrMagoo Mr. McGrew's Christmas Carol]]''.
--->'''Homer:''' Oh, [=McGrew=], once again you've mistaken something for something.
** Homer tries to [[Literature/HowTheGrinchStoleChristmas steal Christmas and gets help from a cute dog]].
* TheyKilledKennyAgain: Hans Moleman gets eaten alive by wolves.
* ToTheTuneOf: "You're a smart one, Homer J."
* WellIntentionedExtremist: Homer tries to get rid of the excess commercialism of the holidays by stealing all the presents and decorations in town and burning them. Naturally, it just pisses everyone off. He does, however, return them afterwards.
* YetAnotherChristmasCarol: Lisa shows Homer that many adaptations of ''Literature/AChristmasCarol'' exist, showing scenes from Christmas episodes of ''Series/StarTrekTheOriginalSeries'' and ''Series/FamilyMatters''.
-->'''Bart:''' TV writers have been milking that goat for years.