This is the first Treehouse of Horror to be officially titled "Treehouse of Horror", and, to date, the last to have 3 separate writers, or 3 separate sets of writers, credited for each story, as every subsequent "Treehouse of Horror" episode has only 1 writer credited.
In this installment, Homer's new hammock makes clones of him, Springfield's new gun ban revives dead outlaws, and Dr. Hibbert invites the Simpsons to his island where everyone is a half-animal, half-human mutant.
Send in the Clones
When Homer's hammock breaks, he buys a new one, disregarding the salesman's warning. It turns out that the hammock clones whoever jumps in it. The clones have diminished mental capacity (and no belly buttons), but with Homer that's not really very noticeable. Homer decides to send the clones to do his chores, like visiting Grandpa Simpson and shopping with Marge. However, when one of the clones decapitates Ned Flanders, Homer decides to abandon them. He takes them out to a cornfield and shoots any clone that admits to knowing the way back (several do, even after he's shot others who knew). He then abandons the hammock—in the same place he abandoned the clones.
The clones promptly use the hammock to make more of themselves, with some imperfect copies (and Peter Griffin). Homer's new Clone Army promptly eats through the cornfield it's in before heading to a brewery. They end up destroying every building in town except Moe's Tavern (which reports record business).
Back in the Simpsons' house, Homer denies knowing anything about the horde, despite Marge and Lisa's skepticism. Later the Simpsons attend a military meeting on what to do about the Homer clones. On hearing Homer's dramatic reaction to seeing that they're out of doughnuts, Lisa thinks of a way to get rid of the clones.
Later, military helicopters dangle gigantic doughnuts in front of the Homer clones (to the tune of Ride of the Valkyries). The clones immediately run after the doughnuts - and off a cliff. The clones are taken care of. Later, Marge snuggles with Homer in bed, but realizes that he doesn't have a belly button - he's a clone, and the real Homer was the first over the cliff. Marge is horrified, but calms down once the clone Homer offers her a backrub.
The Fright to Creep and Scare Harms
Bart and Lisa mourn Goldie the Goldfish at the cemetery. When they walk away from her grave, Lisa sees a grave for William H. Bonney, who was gunned down in 1881. His epitaph is 'I dream of a world without guns'. Lisa decides to make that dream come true, and campaigns to get rid of guns. She succeeds, and all of the inhabitants of Springfield hand over their guns in exchange for cash.
However, as Lisa and the crowd cheer for the achievement of her goal, William "Billy the Kid" Bonney and his outlaw cohorts (yeah, that epitaph was a little misleading) rise from their graves and terrorize the town. They force the Simpsons to put on a show for them at Moe's tavern, with Homer playing piano, Marge playing cello, and Bart and Lisa dancing. Homer is then pulled out by Professor Frink, who's invented something that could save everyone - a time machine. Homer must Set Right What Once Went Wrong. He grabs the time machine and activates it, sending himself to the past. Frink hopes that he doesn't mess up the space-time continuum too much, and then notices that he's got an egg whisk replacing his hand.
In the past, Homer tells the past Springfieldians to grab guns and follow him to the cemetery, where they shoot at the zombies' graves. When Lisa asks what he's doing, he explains that he needs to double-kill the corpses so they won't come back as zombies. Immediately afterwards, they do, but they then run away under the hail of gunfire. As the people of Springfield cheer upon defeating the zombies, a future Homer appears, from a future where gun violence has destroyed the earth. He's shot by Moe, who uses his time machine to go to the past for "caveman hookers".
The Island of Doctor Hibbert
The Simpsons go on vacation to the Island of Lost Souls. Bart wants to know why, and Homer asks "What could be more fun than an island shaped like a big smiley face?" The camera pans out to the island, and we see that it's actually shaped like a giant skull (the eye spaces are giant fires). The Simpsons' plane lands, and they are greeted by Dr. Hibbert. Marge is surprised to see him, as they'd heard that he'd gone mad. He says that yes, he's gone mad - about providing top-notch vacation values! He asks Willie, who's a hairy gorilla-like monster, to help them with their bags.
The family follows Willie through a tropical forest, while mysterious eyes watch them from the bushes. One set of eyes eats another. Marge hears the noise and tells Homer that someone's in trouble, but Homer brushes it off. Later that night, the family eats with Dr. Hibbert, and Marge compliments him on the resort he's running. She asks him to recommend activities. He recommends not asking questions. Lisa says that humans' inquisitive nature is what separates them from animals, and Hibbert goes off on a rant about why man has to be separated from animals. He then uncovers the turkey course - which looks suspiciously like Professor Frink.
When Marge and Homer are getting into bed, she tells him that something creepy is going on with the resort, and decides to do a little sleuthing. She gets out of bed and goes back outside, and discovers a building called the House of Pain. She is immediately captured by Dr. Hibbert, and later, a blue panther with her beehive hairdo pads into Homer's room. The panther scratches him awake. Homer doesn't notice that anything's off and pulls her in bed for "a little lovin'". She scratches him a lot, but he remains oblivious. The noise annoys Bart, who throws an oversized shoe at them.
Later, Homer praises Marge's prowess in bed, still not noticing that she's a panther (even when he talks about her tail). He only catches on when she leaps out of the house to catch a bird. He runs into the House of Pain and searches it for anything to change Marge back. He then finds Flanders, who's been turned into a cow-taur (a female cow-taur, at that). Ned asks Homer to milk him, and afterwards takes him through the forest, where they find a village of half-human half-animal monstrosities.
Homer is horrified that Hibbert has turned them into human guinea pigs, including Bart (spider), Maggie (anteater), and Lisa (owl). Homer makes a speech to inspire them to rebel, but before they can, Hibbert shows up with fox-Mr. Burns. He argues that they were better off now than before. Homer tries to argue that they're nuts. After all, all they can do now is eat, sleep, mate, and roll around in their own filth- actually, Homer thinks that sounds nice, and asks Hibbert to do it to him. He ends up turned into a walrus, and lives at the island with the rest of the half-animal creatures.
From high above, Kang and Kodos note that the island looks like their number 4. They then fly away, and the episode ends.
- 13 Is Unlucky: This is the 13th Treehouse of Horror special.
- Ambiguous Clone Ending: Subverted, as in it's not ambiguous. The real Homer was the first to run off the cliff.
- Bait-and-Switch: Billy the Kid's zombie gang includes "the most evil German of all time"... Kaiser Wilhelm II.note
- Belly Buttonless: Homer's clones. This is how Marge realizes that the Homer in bed with her is a clone.
- Black Is Bigger in Bed: During the gun banning, Lou says this:"Uh, this always made me feel like a man, you know? Now all I got is my enormous genitals."
- Call-Back: The Homer clones (and the real Homer) are all killed by falling down Springfield Gorge, with several of the hits against the edges they make while falling mirroring the ones that happened to Homer in the original episode.
- Clone Army: Homer makes a small one to do his chores. When he abandons both the clones and the hammock used to create them in a cornfield, the clones then use it to become a real army that causes serious devastation to Springfield before the army kills them by luring them off a cliff.
- Clone Degeneration: The clones lack the nuances of the original Homer's personality, possessing even less intelligence and even more ravenous appetites. Though, that may be debatable since the original article was the first one to jump off the cliff following the donuts.
- Constantly Lactating Cow: Ned Flanders is turned into a half-man-half-cow creature (he has his own torso but a cow's body, similar to a centaur) and is in pain from needing to be milked, even though he hasn't recently had calves.
- Devil in Plain Sight: Dr. Hibbert in The Island of Doctor Hibbert.
- End of an Era: XIII is the final Treehouse of Horror episode to be written by three separate writers. Starting with XIV, one single writer handles all three stories.
- Extreme Doormat: Lenny is happy to pick up the tab at Moe's for hundreds of Homer clones.Lenny: Anything for Homers!
- Failed a Spot Check: Homer fails to notice that Marge is a panther for the whole night. He only succeeds in his spot check the next morning, when he sees her leap out the window.
- Four Is Death: Referenced in Kang and Kodos's token appearance:Kang: (seeing the Island of Lost Souls's skull shape) Look at that island shaped like our number four.
Kodos: Makes you think.
- From Bad to Worse: Homer's "mysterious" hammock clones him, and his clones duplicate themselves, and their clones multiply as well, and so on, until eventually it spreads out of control.
- Gender Bender: Ned's cow-half in The Island of Doctor Hibbert is female.
- Interspecies Romance: By the end of The Island of Dr Hibbert, Homer has become a walrus and Marge a panther, they're still together in spite of this.
- Karma Houdini: Dr. Hibbert continues to run his island refuge/laboratory. That said, most of his "victims" really aren't that bothered by what he's done to them so they probably aren't that angry with him in the first place.
- Knocking the Knockoff: Homer clones himself with a magic hammock. Soon, his clones rise up by cloning themselves, causing a few mutations. One of the mutated clones is Peter Griffin.
- Long Game: Bonney's plot to rise and take over after he is dead and buried.
- Mandatory Line: Kang and Kodos have a single line at the end which doesn't really have anything to do with the story.
- Morton's Fork: After Homer goes back in time and prevents the destruction of Springfield's guns (which prevents the zombie outlaws from taking over the town), another Homer from some point farther into the future arrives in a second time machine to warn the people of Springfield that owning guns will somehow cause the destruction of humanity. A fed-up Moe kills him and steals the time machine to go have sex with cavewomen.
- Mythology Gag: One of the clones looks like the Homer from The Tracey Ullman Show shorts. He even says the infamous "Let's all go out for some frosty chocolate milkshakes" line.
- Out-of-Character Moment: Lisa is duped by the epitaph of a man named William Bonney into unleashing zombies upon the town. You'd think someone as book-smart as her would recognize Billy the Kid's real name. (Never mind the biggest thing wrong with the story, which is how in the world did Billy and the other outlaws get interred in Springfield?).
- Lisa also attempts to eat Maggie (now turned into an anteater) in "The Island of Doctor Hibbert," foregoing her vegetarianism. Granted, she was turned into an owl at that point, which leaves her no choice but to adopt a carnivorous diet, but she adapts to it very quickly all things considered. This may be a case of The Mind Is a Plaything of the Body following a very recent transformation and as her parents don't seem angry with her at the end she probably didn't try again.
- The Owl-Knowing One: Lisa is converted into an owl to reflect her intelligence.
- Pacifism Backfire: Lisa's campaign to rid Springfield of guns ends up playing into the zombie outlaws' hands when it leaves the town defenseless against them.
- Painful Transformation: Marge into a blue panther.
- Recognition Failure: It would have saved a lot of grief if one person in Springfield had recognized William Bonney was the real name of Billy the Kid.
- Scared of What's Behind You: Before the first story begins, Bart dresses like the ghost of Maude Flanders for a seance his family is holding with Ned. He thinks they're afraid of him before he realizes the real ghost is behind him.
- Set Right What Once Went Wrong: Homer uses Frink's Time Machine to prevent Billy the Kid's Evil Plan from working.
- Shout-Out: The second Homer that arrives via time travel wears all kinds of futuristic apparel that resemble the stuff seen in the 2015 sequence of Back to the Future Part II.
- Stealth Insult: Peter Griffin appearing as one of Homer's clones.note
- Take That!: When Marge describes the zombie gang as "horrible ghouls from the past", Homer compares them to Grammy awards judges.
- Tempting Fate: After his corn is eaten by Homer clones, Gil tries to find comfort from the fact he's healthy. More Homers show up and eat his flesh.
- Too Dumb to Live:
- Homer's clones. When Homer decided to get rid of the clones, he took them to an empty area and asked which ones knew the way back home. After he shot the first one to raise a hand, other clones did it.
- And then after Homer gets rid of them, he then just tosses the cursed hammock out the window, giving the clones the chance to use it themselves.
- And then Homer himself being the first to chase a doughnut off a cliff when they (again) get rid of the clones.
- Violence Really Is the Answer: After shooing away the zombie gunners via massed gunfire, Lisa laments that guns are probably the answer.
- Whole Plot Reference:
- "Send In The Clones" borrows heavily from the plot of Multiplicity, a comedy that has the main character cloning himself to do some of the tasks and obligations of his workaholic life. It also includes the In-Universe rule not to make a copy of a copy, as they get progressively dumber when that happens.
- "The Island of Doctor Hibbert" is an Affectionate Parody of The Island of Doctor Moreau.
- Would Hurt a Child: The Hole in the Ground Gang do not hesitate to make Bart and Lisa dance at gunpoint.
- Yank the Dog's Chain: Gil finally finds success as a farmer when he grows a successful yield of corn. Then the Homer clones charge in and eat it all. Then they eat Gil, stripping him down to the bone.
- You No Take Candle: The Homer clones talk like this. Bart does the same when Lisa asks if he noticed something wrong with Homer.