School is Hell - Bart and Lisa are transported to a demon-filled alternate universe after Bart reads a set of Aramaic symbols he finds on a desk.
A Clockwork Yellow - Moe's "Clockwork Orange"-style gang is disrupted when Dum (Homer) falls for a girl (Marge) who wants him to give up the thug life.
The Others - The Simpson family are haunted by a family of ghosts, which turn out to be the family from the Tracey Ullman shorts, who were murdered and buried under the house.
Kang and Kodos are hosting a TV special, They talk about the guest stars who will be appearing (such as Sean Penn), only for them to all be chopped up into pieces to spell the title of the episode, Treehouse of Horror XXV.
School is Hell
Principal Skinner has put Bart in detention for spreading rumors about a naked lunch lady. Bored, Bart blows dust off a desk, finding an Aramaic inscription. He brings Lisa to see it; she uses an app to translate it, which transports the pair to Hellroads, where they gain demonic features. Lisa is accepted into a group of mean girls, prompting snow to fall; Lisa is stunned that it would REALLY be a cold day in hell when she was popular. Bart is caught by a two-headed demon that appears to be a hybrid of Skinner and Chalmers, who skins him and tosses him into a classroom. The teacher is asking about how to torture a bank robber, to which Bart gives the ingenious idea of feeding the money to the robber, getting back his skin as a reward. Bart then comes up with the torture of forcing a man to wear an aquarium as pants, and have it filled with piranhas; the screams would power a fan which would release more piranhas.
Lisa finds Bart, showing him a map to escape hell. They use it and unsurprisingly arrive in Mr. Burns' office, where he tells them the Earth time and thanks them for choosing his portal. At home, Bart asks Homer and Marge to let him enroll in Hell. They meet with the principal, who states that Hell encourages and nurtures the students there, winning Marge over. Bart succeeds in all of his classes in Hell, which involve practicing torture and killing Jimbo Jones. He becomes an honor student. For his final test, he must torture Homer. Despite Bart's hesitation, Homer insists as this will make up for all the times he hasn't been there for Bart.
At graduation, the principal has Webster held hostage, as he hates that fact he changed "theatre" to "theater". "BeelzeBart Simpson" graduates as valedictorian, much to the joy of his family. A headless and badly maimed Homer proudly watches.
A Clockwork Yellow
Moe has a Clockwork Orange-style gang in London along with Lenny, Carl and Homer. Homer falls for a girl (Marge) who convinces him to quit, and the gang falls apart. Years later, Moe is attacked at home in a style similar to his gang's former ways, and asks Homer to bring the gang back together. Lenny and Carl, who have become policemen, join them. They attack a masked orgy, similar to the Stanley Kubrick film Eyes Wide Shut, and several other of his films are parodied in a fight sequence. Kubrick is then shown in an editing room and asks for the entire film to be reshot.
In a parody of The Others, The Simpson family find unexplained frosty chocolate milkshakes, blood messages that say "HELP ME" on the mirror, and that their TV only shows the long-running Fox sitcom Married... with Children, and when Homer tries to change the channel, it only shows alternate versions of the sitcom.
After a ghost attacks him in his sleep, Homer summons the ghosts, who are the family's 1987 versions from The Tracey Ullman Show. Homer is attracted to the ghost Marge, who prefers him to the former grumpy ghost Homer, so the jealous living Marge kills herself by cooking her head in the oven to become a ghost. The ghost Homer becomes jealous and bludgeons the living Homer to death with a toaster. Bart fakes suicide to join the ghosts, tricking Lisa into actually killing herself. Her ghost then murders Bart as revenge. Groundskeeper Willie takes the children's corpses to make stew, and he might have killed Maggie. Homer chooses his modern-day wife over the older ghost. The next morning, at the breakfast table, Lisa asks if there could ever be any other incarnations of the Simpsons, due to corporate greed.
The segment finishes with the 1987 version of Homer unsuccessfully trying to photograph a good portrait of the two families together, a direct homage to the short "Family Portrait" from The Tracey Ullman Show, and the photo is ruined.