James Lileks today points out "the filthiest joke ever broadcast on network TV" appears during the "Tomacco" episode of "The Simpsons". He says this sign appears outside a rural store:
SNEED’S FEED AND SEED
(Formerly Chuck’s)
Now that's comedy. I saw the episode and missed the sign completely. Mr Lileks suggests that it's so subtle that the censors must have missed it. In any case, hilarity!