Horror XI" was the first episode to air in November. There have been several references to this in the show, such as in Season 15's "Treehouse of Horror XIV" where Kang looks at a TV Guide and says, "Pathetic humans. They're showing a Halloween episode... in November!" and Kodos replies "Who's still thinking about Halloween? We've already got our Christmas decorations up!" The camera then cuts to a shot of the fireplace with Christmas decorations, and festive Christmas music plays over the opening credits. Season 21's "Treehouse of Horror XX" aired October 18, before the World Series, but the following year's episode, Season 22's "Treehouse of Horror XXI", aired on November 7. Season 23's "Treehouse of Horror XXII aired on October 30, however, as the World Series (which went the maximum of seven games) had concluded on October 28. Subsequent Treehouse of Horror episodes have premiered in the month of October. The 31st season included a Thanksgiving-themed spinoff, "Thanksgiving of Horror". The 32nd season however pushed "Treehouse of Horror XXXI" to November 1, 2020 because the National League Championship Series went into Game 7, with the World Series that followed stretching to Game 6, resulting in Fox airing Treehouse after Halloween for the first time since 2010. Citytv in Canada however aired the episode as originally scheduled. "Treehouse of Horror XXXII", aired in 2021 on October 10 due to the MLB post-season running into the first week of November, and to avoid airing in November again due to the World Series overrun, and with no World Series game being played on a Sunday, "Treehouse of Horror XXXIII" aired in 2022 on October 30. In past years prior to 2011, however, new shows have been known to have aired exclusively on the West Coast at the appropriate time prior to the rest of the nation’s airing after Halloween. Merchandise There has been a variety of merchandise based on the Treehouse of Horror episodes, including books, action figures, comic books, video games, DVDs and a "Treehouse of Horror" version of Hasbro's board game Monopoly. Although every Treehouse of Horror episode until "Treehouse of Horror XIX" has been released along with its season in a boxset, in 2003, The Simpsons: Treehouse of Horror DVD was released. It includes Treehouse of Horrors V, VI, VII and XII. A Treehouse of Horror comic book was published annually from 1995-2017, and collected into several books, including