take place outside the normal continuity of the show. Although the Treehouse series is meant to be seen on Halloween, this changed by the 2000s (and again in 2020), when new installments have premiered after Halloween due to Fox's current contract with Major League Baseball's World Series. Prior to 2020 (between 2011 and 2019), every Treehouse of Horror episode had aired in October. Humor The show's humor turns on cultural references that cover a wide spectrum of society so that viewers from all generations can enjoy the show. Such references, for example, come from movies, television, music, literature, science, and history. The animators also regularly add jokes or sight gags into the show's background via humorous or incongruous bits of text in signs, newspapers, billboards, and elsewhere. The audience may often not notice the visual jokes in a single viewing. Some are so fleeting that they become apparent only by pausing a video recording of the show or viewing it in slow motion. Kristin Thompson argues that The Simpsons uses a "flurry of cultural references, intentionally inconsistent characterization, and considerable self-reflexivity about television conventions and the status of the programme as a television show." One of Bart's early hallmarks was his prank calls to Moe's Tavern owner Moe Szyslak in which Bart calls Moe and asks for a gag name. Moe tries to find that person in the bar, but soon realizes it is a prank call and angrily threatens Bart. These calls were apparently based on a series of prank calls known as the Tube Bar recordings, though Groening has denied any causal connection. Moe was based partly on Tube Bar owner Louis "Red" Deutsch, whose often profane responses inspired Moe's violent side. As the series progressed, it became more difficult for the writers to come up with a fake name and to write Moe's angry response, and the pranks were dropped as a regular joke during the fourth season. The Simpsons also often includes self-referential humor. The most common form is jokes about Fox Broadcasting. For example, the episode "She Used to Be My Girl" included a scene in which a Fox News Channel van drove down the street while displaying a large "Bush Cheney 2004" banner and playing Queen's "We Are the Champions", in reference to the 2004 U.S. presidential election and claims of conservative bias in Fox News. The show uses catchphrases, and most of the