Treehouse of Horror Facts

The first Halloween Simpsons special was in the second season (1990) and was called "Treehouse of Horror" and featured Bart and Lisa (and Maggie) telling stories in Bart's treehouse.
The first story parodies the Amityville Horror, the second parodies the famous Twilight zone episode "To Serve Man" and features the very first appearance of Kang and Kodos, and lastly is the ever popular James Earl Jones reading "The Raven" (omitting stanzas 5 and 8 through 16). Good times.

So this yearly custom became an annual tradition and every Halloween special since has been named after the first Treehouse of Horror. The first 5 featured warnings in the opening segment as well as a fly through cemetery with amusing tombstones (TofH V had a tombstone that said "amusing tombstones"), which was subsequently ditched for other forms of opening clips.

The Halloween episodes usually have special "scary names" credits (inspired by EC Comics, which would do this sometimes). These were dropped in XII and XIII because they were too hard, but everyone complained so they brought them back. Also, TofH II through X had Halloween-y couch gags, in season 11 they broke that run by doing a Munsters opening parody.

All the Halloween episodes have 3 separate stories. The first four also had overarching settings: treehouse stories, candy induced nightmares, Halloween party stories, and scary paintings (a spoof of Night Gallery, which aired in the early 70s, by the same guy who did Twilight Zone). But these were dropped because they ate up too much time. Most of the stories are parodies (of scary movies, TV shows, books, etc.) and, besides movies in general (everything from The Shining to Harry Potter), the single most commonly parodied source is "Twilight Zone" with at least 8 parody segments to date ("To Serve Man", "A Small Talent for War","Living Doll", "Nightmare at 20,000 Feet","Little Girl Lost", and "The Little People", "It's a Good Life", and "A Kind of a Stopwatch"). FYI: They parody Twilight Zone in regular episodes too ("Bart's Comet" is a parody of "The Shelter", "Strong Arms of the Ma" spoofs "Time Enough at Last", etc.) .


p.s. The new Halloween episode, Treehouse of Horror XIX, airs tomorrow (continuing FOX's schedule of airing Halloween episodes in November because of their contract with the World Series). A segment of the episode (with Spanish subtitles) has been leaked, which features Homer running afoul of a rigged voting machine. Mayhem ensues.