My favourite Simpsons scenes are also from a Halloween episode:
The Simpsons are visiting a creepy mansion, owned by Mr Burns, who is showing them round.
(Elevator door opens, blood begins to stream out of it)
Mr Burns: "That's odd, the blood usually gets off at the second floor"
Mr Burns: "This house was the scene of three murders, an ancient Indian burial and five John Denver Christmas specials"
Homer (creeped out): "Ugggghhh, John Denver"