Treehouse of Horror is a series of annual Halloween-themed anthology episodes of the American animated sitcom The Simpsons. Also known as The Simpsons Halloween Specials, each episode typically consists of three separate, self-contained segments. Each segment involves the Simpson family in some comical horror, science fiction, or supernatural setting; plot elements operate beyond the show's normal continuity, with segments exaggeratedly more morbid and violent than a typical Simpsons episode. With 36 episodes as of 2025, each Treehouse of Horror episode is numbered in Roman numerals, one less than the respective season it is in; the tradition began with the second season.
The eponymous first installment "Treehouse of Horror" aired on October 25, 1990, during the second season, broadly inspired by EC Comics horror tales. In addition to parodies of horror, science fiction, and fantasy films, episodes include the recurring alien characters Kang and Kodos, unique opening sequences, and 'scary' pseudonyms in the credits. Treehouse of Horror episodes have earned high ratings and broad popularity, spawning a steady stream of merchandise, including a comic book series that ran from 1995 to 2017.
Segments Treehouse of Horror episodes typically consist of four parts: an opening and Halloween-themed version of the credits, followed by three segments. These segments usually have a horror, science fiction or fantasy theme and quite often are parodies of films, novels, plays, television shows, Twilight Zone episodes, or old issues of EC Comics. Although they are sometimes connected by "wraparounds", the three segments rarely have any kind of continuing connection within the episode. Some have recurring elements, such as "Treehouse of Horror V", in which Groundskeeper Willie is killed by an axe in all three segments. The episodes are considered to be non-canon, which means they take place outside the normal continuity of the show.
The number of episodes of Treehouse of Horrors matches the number of series of the show: there are no such specials in season 1, two in season 34 and one in each other season. From "Treehouse of Horror" to "Treehouse of Horror XIII" and resuming with "Treehouse of Horror XXXIII", all three segments were written by different writers. In some cases there was a fourth writer who wrote the opening and wraparound segments. For the original "Treehouse of Horror", there were three different directors for the episode. From season 15's "Treehouse of Horror XIV" to season 33's "Treehouse of Horror XXXII", however, only one writer was credited with writing each Treehouse of Horror episode. "Treehouse of Horror XXXII" featured five segments. One of the season 34 Treehouse of Horror specials, "Not It", is distinguished by its uncharacteristic title and one full-length segment (divided in the two parts).
On occasion, the episodes will be used to showcase special animation, such as the "Treehouse of Horror VI" segment "Homer3", in which a computer-animated Homer is shown in a non-animated setting. At the time (1995), it was unusual for a television show to use such animation. The segment was executive producer Bill Oakley's idea and included live-action directed by David Mirkin. "Treehouse of Horror XX" included the segment "There's No Business Like Moe Business", which was the first to be musically themed.
Traditions
Opening sequence
The first, second, and fifth Treehouse of Horror episodes open with Marge standing on a stage and warning parents about the content of the episode, advising them to put their children to bed. The warning in the first episode was put in as a sincere effort to warn young viewers, as the producers felt it was somewhat scary. The entire segment was a parody of Edward Van Sloan's pre-credits warning from the 1931 film Frankenstein. Marge's warnings quickly became a burden to write, particularly because – as she herself noted – they were mostly ignored, so after "Treehouse of Horror V", they were dropped. The segment returned in the season 31 episode "Thanksgiving of Horror".
Other Treehouse of Horror episodes have opened with parodies; for example, "Treehouse of Horror III" had Homer introduce the episode in a manner similar to Alfred Hitchcock in Alfred Hitchcock Presents, "Treehouse of Horror IV" had Bart introduce the episode and segments in a manner similar to Night Gallery, and "Treehouse of Horror V" featured a parody of The Outer Limits. The sixth and seventh episodes featured short clips with no lines because the episodes had run long, and longer segments were cut. Following "Treehouse of Horror VII", the opening has been upwards of a minute long and sometimes featured an introduction by a character, such as Mr. Burns in "Treehouse of Horror XVII" or included over-the-top violence, such as "Treehouse of Horror VIII" (which showed a Fox Network censor being brutally murdered) and "Treehouse of Horror XIV" (which showed the Simpson family killing each other).
In the opening segment of the first five episodes, the camera zooms through a cemetery where tombstones with humorous epitaphs can be seen. These messages include the names of canceled shows from the previous season, deceased celebrities such as Walt Disney and Jim Morrison, and a tombstone with an inscription that read "TV violence" that was riddled with bullets as the camera panned on it. They were last used in "Treehouse of Horror V", which included a solitary tombstone with the words "Amusing Tombstones" to signal this. The tombstone gags were easy for the writers in the first episode, but like Marge's warnings, they eventually got more difficult to write, so they were abandoned. Another reason they were dropped was that the tombstones would list television shows that had been canceled the previous season; after a few years, several of the shows that were canceled were produced by former Simpsons writers. However, after two decades, this gag made a brief comeback in "Treehouse of Horror XXIX" at the very beginning, this time appearing before the main opening sequence and title.
While the early Treehouse of Horror episodes featured a Halloween themed opening sequence, the later ones only included the title and the "created by" and "developed by" credits. Every episode between "Treehouse of Horror III" and "Treehouse of Horror X" featured a couch gag with a Halloween theme, including the Simpson family dressed as skeletons, zombies, and characters from previous Halloween episodes.
Wraparounds The first four Treehouse of Horror episodes had brief wraparounds that occurred before each segment and loosely tied together all three stories. "Treehouse of Horror" was the only one that actually included a treehouse as a setting. In that episode, Bart and Lisa sat in it telling stories to each other. "Treehouse of Horror II" presented all of the segments as being nightmares of Lisa, Bart and Homer; "Treehouse of Horror III" had Lisa, Bart and Grampa telling stories at a Halloween party; and "Treehouse of Horror IV" is presented by Bart in a parody of Rod Serling's Night Gallery. After a few years, the amount of broadcast time for an episode was shortened, allowing less time to tell a proper story. There were no wraparounds for "Treehouse of Horror V" because they had been cut to make more time for the segments. Following that, the writers permanently dropped them (excluding "Treehouse of Horror Presents: Simpsons Wicked This Way Comes").
Kang and Kodos
Two characters that are virtually exclusive to the Treehouse of Horror series are Kang and Kodos, a pair of large green space aliens who were introduced in the "Hungry are the Damned" segment of "Treehouse of Horror". Kang and Kodos have since appeared in every Treehouse of Horror episode, often in cameos. In some episodes, they only appear in the opening segment, but often they will make a cameo appearance in the middle of a different story. For example, a story about zombies attacking the town briefly cuts to them in their space ship, watching the events and laughing maniacally at the Earthlings' suffering. The action then switches back to the actual story. According to Al Jean in 2022, an unofficial rule is that they must be in every episode, although quite often they will be forgotten and are added at the last moment, resulting in only a brief appearance. Their scene in "Treehouse of Horror VIII" nearly did not make the final cut of the episode, but David X. Cohen managed to persuade the producers to leave the scene in.
Kang and Kodos were prominent characters in the 2015 episode "The Man Who Came to Be Dinner", which was not Halloween themed.
Scary names
Beginning with "Treehouse of Horror II", the producers decided to give the cast and crew of the show 'scary names' in the opening and closing credits. Although the names quickly became more silly than scary, there have been a wide variety of special credits, from simple names like "Bat Groening" or "Chains Hell Brooks" to complex ones like "Dan CastellanetarghaGAHEGGA (Smash) Gurgle Mr. Hyde".
The idea for 'scary names' came from executive producer Al Jean, who was inspired by EC Comics because some of the issues also used 'scary' alternate names. The "scary names" became such a burden to write that they were cut for "Treehouse of Horror XII" and "Treehouse of Horror XIII", but after hearing complaints from the fans, Jean decided to bring them back. Matt Groening's rule for the "scary names" is that they cannot be longer than a person's real name, but this is rarely followed by anyone else.
Cultural references References to films, novels, plays, television shows, and other media are commonly featured, and many segments have been parodies of a specific work in the horror, science fiction, or fantasy genre. Many segments are spoofs of episodes of The Twilight Zone, and entire segments will be based on a single episode. Some of the Twilight Zone episodes parodied include "A Kind of a Stopwatch", "To Serve Man", "A Small Talent for War", "Living Doll", "Nightmare at 20,000 Feet", "Little Girl Lost", and "The Little People". The "Bart's Nightmare" segment of "Treehouse of Horror II" parodies the episode "It's a Good Life" and is even presented in a format similar to an episode of The Twilight Zone.
Horror and thriller films parodied include The Exorcist, The Amityville Horror, King Kong, Night of the Living Dead, The Shining, A Nightmare on Elm Street, The Fly, Paranormal Activity, and Dead Calm. Robert Englund had a cameo appearance in "Treehouse of Horror IX" as his character from A Nightmare on Elm Street, Freddy Krueger. Science fiction films have also occasionally been used as inspiration for segments, and in later episodes, many of the segments were based more on science fiction than horror. Science fiction works parodied include The Omega Man, the novel Nineteen Eighty-Four, E.T. the Extra-Terrestrial, The Island of Doctor Moreau, and Orson Welles's The War of the Worlds radio broadcast. In "Treehouse of Horror", Edgar Allan Poe's poem "The Raven" is read by James Earl Jones, while the parts are acted by various characters.
From the late 1990s, parodies have included films and television specials in more varied genres, including Mr. & Mrs. Smith; It's the Great Pumpkin, Charlie Brown; Transformers; Sweeney Todd; the Twilight film series; and Jumanji.
Production
The first Treehouse of Horror installment aired in 1990 as part of the second season, and its on-screen title was "The Simpsons Halloween Special". ("Treehouse of Horror XIII" was the first to feature "Treehouse of Horror" in the on-screen title.) It was inspired by EC Comics Horror tales. Although every episode is entitled Treehouse of Horror, the first was the only episode that actually used the treehouse motif. During production of the first episode, Matt Groening was nervous about "The Raven" segment, and felt it would be "the worst, most pretentious thing [they had] ever done."