Treehouse of Horror XX (Season 21; Oct. 18, 2009)
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My old review mentioned Mr. Burns making an announcement at a sporting event, about a half-time sneak peek of the forthcoming movie A Christmas Carol. But apparently that's not in the actual episode, and I don't see it mentioned online, so maybe it was just a commercial that happened to air right before the episode. (I found a partial clip on YouTube.) I should also mention that this was the first time in ten years that Treehouse of Horror aired before Halloween instead of after it.

Intro: Frankenstein's monster, the Mummy, Wolfman, and Dracula go out on Halloween and dress in more modern costumes (Harry Potter, Iron Man, Spongebob Squarepants, and I'm guessing Jack Sparrow), and go to the Simpsons' Halloween party. And there's a surprise ending which is amusing.

Dial "M" for Murder or Press "#" to Return to Main Menu: In a black & white parody of Alfred Hitchcock films (mainly Strangers on a Train), Bart proposes he and Lisa criss-cross crimes. He kills Ms. Hoover, expecting Lisa to kill Mrs. Krabappel, though she doesn't want to do that. It's a pretty decent segment.

Don't Have a Cow, Mankind: In a parody of 28 Days Later, Krusty introduces a new product called Burger², which turns people into zombies (or "munchers"). But when Bart turns out to be immune, his family tries to get him to the safe zone, with help from Apu. There are a bunch of good gags.

There's No Business Like Moe Business: In a musical parody of Sweeney Todd, the show stages a play wherein Moe uses Homer's blood as a secret ingredient in his beer. He also tries to convince Marge that Homer has left her and that she should date Moe, instead. It's mostly a decent segment, I guess. Also, Kodos and Kang are in the audience watching the play.