The 30th Treehouse of Horror features a demon Maggie, a mission to rescue Milhouse from another dimension, dead-Homer's spirit trying on some new bodies for size and Selma finally finding love in an unlikely place - the alien in the basement.
At the Springfield General Hospital, we that the third baby Marge had was actually a boy, but Homer didn't want another boy, as Bart is bad enough. Dr. Hibbert offers that he adopts Maggie, who actually has demon-like powers, which she uses to choke Hibbert with his stethoscope and burn him.
We see Maggie use her powers to spin around stuffed animals heads, make them vomit up their stuffing, and make Kearney and Jimbo hang themselves.
Ned sees Maggie's devilish abilities and attempts to kill her at a abandoned church. Homer and Marge try to stop him, but Ned shows them that Maggie ¨bears the mark of the beast¨. He shows, under her hair, a mark that looks like Mickey Mouse. This is the wrong mark, however, and the real mark is the numbers ¨666¨, the number of the Devil.
Before Ned can kill Maggie, she rises in the air, and breaks open the roof of the church. Homer states that Maggie still better than another boy, and all three them get giant wooden stakes through their hearts. The classic Treehouse of Horror logo appears, with the staked Ned, Marge, and Homer appearing as the Roman Numerals (XXX).