"Treehose of Horror XX" is a Halloween-themed episode from the twenty-first season of the animated comedy series The Simpsons. It was first broadcast in the United States on the Fox Network on October 18, 2009, in Australia on Channel 10 on November 3, 2009 and in the UK on Sky 1 on February 4, 2010. The episode won an Annie Award for Best Writing in a Television Production.
The program is made up of three segments: "Dial 'M' for Murder (or Press # to Return to Main Menu)", "Don't Have a Cow, Mankind" and "There's No Business Like Moe Business". The plot of the first segment is based on the 1951 Alfred Hitchcock movie Strangers on a Train and contains several references to other Hitchcock films. The second segment is a parody of 28 Days Later and other zombie movies. The third segment spoofs the musical Sweeney Todd.
On Halloween night, four monsters - Dracula, Frankenstein's monster, a mummy and a werewolf - are prowling the streets of Springfield. They are mistaken for costume-wearers and are teased for choosing old-fashioned costumes. They decide to go to a shop to get some popular modern Halloween costumes. Dracula dreses as Iron Man, Frankenstein's monster as SpongeBob, the mummy as the pirate Captain Jack Sparrow and the werewolf as Harry Potter. They go to the Simpsons' Halloween party and begin flirting with some women. The monsters' wives arrive and complain that their husbands are cheating on them instead of killing children. Homer Simpson tries to mediate but gets his head cut off, the Roman numerals "XX" appearing in his eyes.
"Dial 'M' For Murder (or Press # to Return to Main Menu)"
Lisa Simpson gets angry at her teacher Miss Hoover when she is not chosen to represent her class at a reading event. She is put in detention for disrupting the class. Her brother Bart is in detention with her. He suggests to Lisa that they should take revenge on each other's teachers, saying that he will do a "ding dong ditch" on Miss Hoover if Lisa will do the same to Bart's teacher Mrs. Krabappel. Lisa rings Mrs. Krabappel's doorbell and runs away but then discovers that Bart has killed Miss Hoover and dumped her body in a ditch.
When she tries to report her brother to Principal Skinner, Lisa finds that Bart has murdered him too. She decides that she will have to put a stop to Bart's murderous ways by killing him. She chases him with a knife and pursues him onto a merry-go-round. Having decided not to kill Bart after all, Lisa throws the knife into the air. It plummets into Bart and kills him. Lisa and Mrs. Krabappel then walk away smiling.
The segment, which references several of the movies of Alfred Hitchcock, is in black and white.
"Don't Have a Cow, Mankind"
Krusty Burger launches a new hamburger made from the meat of cannibalistic cows. Anybody who eats one of the burgers turns into a pale-skinned, red-eyed, zombie-like creature called a Muncher. Anybody who is bitten by a Muncher becomes a Muncher too.
Twenty-eight days later, most of the people of Springfield have been transformed into Munchers. The Simpsons have boarded up their house for protection. Bart is hungry but refuses to eat the fruit in the house. He sneaks out, eats one of the new Krusty Burger hamburgers but does not change into a Muncher because he has a natural immunity.
The Simpsons' family doctor advises them to get to the safe zone, so that Bart's immunity can be used to develop a cure. On the journey, Homer gets bitten, turns into a Muncher and is locked in a cage for safety.
When they arrive at the safe zone, a soldier tells the Simpsons that they will have to eat Bart in order to gain his immunity. However, it is discovered that it is not necessary to kill Bart after all. Eating soup from an enormous pot that Bart has bathed in immunizes people and cures all those who had been transformed into Munchers. Homer remains uncured and still locked in the cage because he refuses to eat any soup which his son has bathed in.
"There's No Business Like Moe Business"
Moe the bartender is sad and lonely because he does not have a girlfriend. He feels jealous whenever he sees Homer and Marge Simpson together.
Homer accidentally falls into the basement of Moe's Tavern and becomes impaled on Moe's microbrewing equipment. Homer's blood slowly gets pumped out of him and goes into Moe's home-brewed beer. The blood turns out to be the missing ingredient which makes Moe's new beer a huge success. Everyone who drinks the beer feels warm, cozy and secure. Moe uses his beer in an attempt to woo Marge, telling her that Homer left her to see what it was like to be gay.
When Homer emerges alive from the basement, Marge is happy to return to him, even though he has a pump from the microbrewing machine through his back.