Homer makes a deal with the devil (Ned Flanders, of course), trading his soul for a donut. Family lawyer Lionel Hutz argues for Homer's freedom before a jury of the damned that includes John Wilkes Booth, the 1976 Philadelphia Flyers and a not-yet-dead-at-the-time Richard Nixon.
A botched toaster repair sends Homer back in time to the age of the dinosaurs. He accidentally changes history when he kills a mosquito, creating a butterfly effect that leads to Ned Flanders becoming the unquestioned lord and master of the world.
In an homage to a famous The Twilight Zone episode, Bart discovers that a gremlin is sabotaging his school bus. No one heeds Bart's warnings, however -- Principal Skinner tells him, "I've received word that a student is using his imagination, and I'm here to put a stop to it."
When Groundskeeper Willie dies in a fire during a school board meeting, the Scotsman vows revenge on the children of Springfield. He then starts appearing in their dreams, killing them off one by one -- until the Simpsons get involved.
When Maggie's "baby legs" fall off, its revealed that her real father is actually the alien Kang. The Simpsons then appear on The Jerry Springer Show to settle their baby mama drama, with predictably disastrous results.
The story starts with Lisa freeing a dolphin from a Sea World-like marine park. But the good deed turns sour when the freed dolphin urges his species to rise up against humanity and get revenge for our numerous transgressions against them.
The Simpsons mansion-sit for Mr. Burns without bothering to ask whether there's any cable TV or beer. The lack of entertainment causes Homer to go crazy, whipped up into a murderous frenzy by a ghostly Moe Szyslak.
Bart discovers that he was born a conjoined twin and that his "evil" brother Hugo is kept locked in the attic. Hugo then gets loose and devises a plan to physically re-attach himself to Bart.
Homer buys an evil Krusty doll for Bart's birthday -- a gift that quickly turns homicidal. It's a good lesson to us all: Don't buy gifts from a store named "House of Evil," even if your purchase does come with a free frogurt.
When Homer discovers that his new hammock creates clones of whoever sits in it, he creates an army of Homers to take over his fatherly responsibilities. Things go pear-shaped when the clones begin making copies of themselves, destroying all of Springfield (save for Moe's Tavern, which enjoys record business).
When the staff of Springfield Elementary learns that human flesh tastes better than the grade-F meat otherwise being used in the cafeteria ("mostly circus animals, some filler") students start disappearing one by one.
After eating too much Halloween candy, Bart dreams a world where he has the ability to both read minds and alter reality to his whim. An omnipowerful Bart, it turns out, is an evil Bart -- anyone who thinks ill about him winds up being transformed into a bizarre creature, Homer included.
Bart and Lisa make a pact -- Bart will ding-dong-ditch Lisa's teacher, Ms. Hoover, if Lisa will do the same to Ms. Krabappel. But while Lisa subjects Bart's teacher to a juvenile door-bell prank, Bart instead beheads the "ding-dong" Hoover and throws her body in a ditch.
After stealing Lard Lad's giant metal donut, a bolt of lightning brings the Springfield advertising icon to life. Other ads in town run amok as well, including a 50-foot-tall version of anchorman Kent Brockman.
To escape a visit from Marge's sisters, Patty and Selma, Homer stumbles into the mysterious "third dimension."
When Snake is given the electric chair for smoking inside the Kwik-E-Mart, his organs are harvested for transplant. Homer receives Snake's hair, which carries with it the revenge-bent spirit of the deceased criminal.
In this black-and-white short, a 1930s-era Mr. Burns travels to Ape Island in a bid to capture the oversized King Homer for a stage show. The show earns poor reviews when Homer goes mad, eats Shirley Temple, kidnaps Marge and runs amok through downtown Springfield.
During a trip to Morocco, Homer Simpson purchases a cursed monkey paw with the power to grant wishes. When Lisa uses the paw to ask for world peace, aliens Kodos and Kang conquer the newly weapon-free Earth using only a club and a slingshot.
Everything goes great for the Simpsons when they install the Ultrahouse CPU home automation system -- at least for a little while. But when Homer inexplicably mentions that his death would free up Marge to get romantic with either "man or machine," Ultrahouse plots Homie's demise.
In this long-awaited parody of the Peanuts Great Pumpkin special, Milhouse persuades Lisa to spend her Halloween waiting for the arrival of the Grand Pumpkin. When the Grand Pumpkin eventually shows up, he seeks revenge for all the atrocities being committed against his kind during the holiday.
During the 1996 presidential election campaign, aliens Kodos and Kang bodysnatch Bill Clinton and Bob Dole in a bid to take over the Earth. Homer exposes the ruse, but America stands by the two-party system anyway, electing Kang over Kodos and the human Ross Perot.
Aliens Kodos and Kang abduct the entire Simpson family with the stated purpose of bringing them to a massive feast in their honor on planet Rigel IV. Lisa quickly becomes suspicious of the aliens' generosity, believing that her family is being fattened up to be cooked as the main course.
During a discount vacation on Dr. Hibbert's private island, Marge is captured and turned into a catwoman. Homer then discovers much of Springfield has become "manimals" at the hands of Hibbert, and learns that life as a half-animal might not be so bad after all.
A mixture of soda, static electricity, and a human tooth somehow sparks the creation of new life in miniature -- not too bad for a science fair project. The inhabitants of the tooth world quickly evolve and grow to worship Lisa as a god, while Bart is seen as the destroyer.
An attempt by the Simpsons kids to resurrect beloved cat Snowball I inadvertently resurrects every single dead body in the town of Springfield. "Is this the end for Zombie Shakespeare?!"
The final sketch of the original Treehouse of Horror special is a retelling of the Edgar Allen Poe poem The Raven, with a twist -- Bart plays the titular part while Homer serves as the poem's main human character.