Maybe Treehouse of Horror 3 from Season 4 (features the evil Krusty doll segment with the immortal frozen yoghurt scene, the Homer as King Kong parody and the Night of the Living Dead spoof).
Just... Too many good jokes:
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Carl: Hey, I heard we're goin' to Ape Island.
Lenny: Yeah, to capture a giant ape. I wished we were going to Candy Apple Island.
Charlie: Candy Apple Island? What do they got there?
Carl: Apes. But they're not so big.
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Mr. Burns: What do you think, Smithers?
Smithers: I think women and sea men don't mix.
Mr. Burns: Yes we know what you think.
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Lisa: Dad, we did something very bad!
Homer: Did you wreck the car?
Bart: No
Homer: Did you raise the dead?
Lisa: Yes!
Homer: But the car's okay?
Lisa and
Bart: Uh-huh.
Homer: All right then.
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Treehouse of Horror V (The Shinning, Time and Punishment and Nightmare Cafeteria) and Treehouse of Horror IV (The Devil and Homer Simpson, Terror at 5 1⁄2 Feet and Bart Simpson's Dracula) are also near perfect. The bit at the end of V with the dance number set to the gas that turns peoples skin inside out is so bizarrely memorable: