They don't come any more eye-opening than Cartman's revenge on Scott Tennorman.
Professional Moldy Fig/Curmudgeon
Fritz The Cat and its sequel had some of the most eye-opening gags I have ever seen.
"They say I'm old fashioned, and live in the past, but sometimes I think progress progresses too fast."
I recently rewatched an episode of Tiny Toon Adventures in which Sweetie got walloped while trying to eat Bookworm and said "Now I know how Robin Givens feels." My jaw hit the ground. Almost nothing in fiction offends me, this was more out of surprise than anything. What Do You Mean, It's for Kids? indeed.
EDIT: slightly off topic, but there are zero Warner Brothers examples on the trope page I just linked. Do I detect some trollish vandalism or is there a reason for that?
EDIT 2: Whatever, I located the deleted examples and restored them anyways. 
edited 26th Jan '15 11:40:05 AM by redhed311
Let\'s talk about that I call Eye-Opener gags. These are shock value jokes or gags that make your eyes pop open, whether you find it funny or not.
\'\'Family Guy\'\' uses these often, usually when they make light of something serious or tragic (i.e. the Lockerbie joke from \"Go, Stewie, Go!\"), or make mention of something sexual or disgusting (i.e. the anal beads joke from \"Cool Hand Peter\").