"Treehouse of Horror XIII" is a Halloween-themed episode from the fourteenth season of the animated comedy series The Simpsons. It was first broadcast in the United States on the Fox network on November 3, 2002. It was the first Halloween episode of The Simpsons to be identified as "Treehouse of Horror" rather than "The Simpsons Halloween Special" during the title sequence.
In common with all of the previous Simpsons Halloween specials, the program is made up of three self-contained stories; "Send in the Clones", "The Fright to Creep and Scare Harms" and "The Island of Dr. Hibbert". In the first story, Homer Simpson gains the ability to clone himself but soon finds the clones impossible to control. In the second story, the town of Springfield is attacked by the zombies of famous deceased criminals. The final story, a parody of H.G. Wells' 1896 science-fiction novel The Island of Dr. Moreau and its various movie adaptations, involves people being transformed into animals.
The Simpson family and their neighbor Ned Flanders hold a séance to try to contact Flanders' recently deceased wife Maude. Bart Simpson dresses up and pretends to be Maude's ghost. The real ghost of Maude arrives and transforms into a hideous ghoul.
"Send in the Clones"
When Homer Simpson's hammock breaks, he buys a new one from a passing salesman. He is warned that the hammock he has bought carries a curse. Homer finds that the hammock produces a clone of anyone who lies in it. The first clone of Homer appears identical to him in every way but has no navel. Homer creates several clones of himself and uses them to perform all of the chores that he does not want to do.
Homer soon discovers that the clones are stupider than he is. When he indicates that one of the clones should return a borrowed chainsaw to neighbor Ned Flanders, the clone murders Flanders with the chainsaw instead. Homer drives the clones and the hammock out to a distant cornfield and abandons them there.
The clones use the hammock to make more copies of themselves. Many of the new clones appear as mutated versions of Homer (including a frosted chocolate milkshake-loving one one which looks like the original 1987 version of Homer Simpson from shorts on The Tracey Ullman Show and one which looks like Peter Griffin from Family Guy). The clones attack the town of Springfield, destroying all the buildings except for Moe's Tavern.
The army are brought in to solve the problem. Knowing her father's love of doughnuts, Lisa Simpson suggests that helicopters carrying giant doughnuts could be used to lure the Homer clones into falling down a deep gorge.
The segment ends with Marge Simpson discovering that the man she has taken for husband is not the real Homer but one of his clones, the real Homer having been the first to leap into the gorge after a giant doughnut. However, when the clone offers Marge a back rub, she ceases to care.
"The Fright to Creep and Scare Harms"
On a visit to Springfield Cemetery, Lisa Simpson notices the grave of William Bonny. The inscription on his gravestone says that Bonny lost his life at a young age because of gun violence and dreamed of a world without guns. Lisa is inspired to start an anti-gun campaign in his memory. The campaign is so successful that all the people of Springfield stop carrying guns, even the police.
As soon as the town is defenseless, the zombie of William Bonny, better known as Billy the Kid, rises from the grave. He and his gang of other zombie criminals, including Jesse James, the Sundance Kid and Kaiser Wilhelm II, terrorize the town.
Scientist Professor Frink attempts to solve the zombie problem by inventing a time machine. Homer Simpson travels back to a time before the gun ban. He tells the people of Springfield to fire guns at the criminals' graves, causing the zombies to flee. After everything appears to have been put right, a Homer from the future arrives in the present. He announces that guns will destroy the world but Moe the bartender shoots him.
"The Island of Dr. Hibbert"
In a parody of The Island of Dr. Moreau, the Simpson family go on vacation to the "Island of Lost Souls". They discover that Dr. Hibbert, their former family doctor, is in charge of the resort. Marge Simpson whispers that Hibbert is rumored to have gone mad.
A suspicious Marge investigates. She is captured by Dr. Hibbert and transformed into a blue puma. Looking for a cure for Marge, her husband Homer is aided by their neighbor Ned Flanders, who has been transformed into a centaur like creature with the body of a cow. Homer discovers that many of the people that he knows have been changed into animals, including his children. His son Bart has been changed into a spider, his baby daughter Maggie has been changed into an anteater and his other daughter Lisa has been changed into an eagle, which almost eats the anteater Maggie.
Homer is horrified by what he sees at first. He then realizes that the life which animals lead, eating, sleeping, mating and rolling around in their own filth, suits him perfectly and he is happy to be transformed into a walrus. He and the other animal-people spend the rest of their lives happily relaxing by Dr. Hibbert's swimming pool.
The segment ends with the aliens Kang and Kodos observing Dr. Hibbert's skull shaped island. They comment that it looks like the symbol they use for "4 " on their planet, possibly a reference to the word for "four" sounding similar to the word for "death' in Chinese and Japanese.