Any examples of cartoon comments only adults got?
There's a Popeye cartoon, one of the very early ones.
He's in a nightclub dancing,( the Samba I think), in front of Bluto who says "Now hold on there partner, I always took you to be a straight shooter"
Ahead of their time and over kids heads don't you think?
I don’t think that the Popeye/Bluto incident is actually ahead of it’s time. Maybe it just slipped past the censors, maybe it meant something in its time other than it does now.
One Elmer Fudd and Bugs Bunny cartoon is on a "Ring of the Niebelungen" theme with the end roughly resembling "Die Gotterdammerung" (Twilight of the Gods) where Fudd manages to actually kill Bugs.
One of the cartoonists who worked at Warner Bros. in the "Golden Age" said that Jack Warner never crossed their doorway and just let them get on with it. He said that their cartoons were directed at adults more than at children. But the jokes were rarely of a sexual kind, that would have been picked up by the censors who were quite active when most Warner Bros stuff was made. Cartoons were made for cinema audiences half of whom were adults and would not have sat still for real kid stuff.
More recently
In one Simpsons episode they send their baby to the "Ayn Rand" nursery school or child minding centre, that goes right over the head of a lot of people, let alone children.
Another episode has Bart, as a last request, asking Sideshow Bob to sing the entire score of the Gilbert & Sullivan musical "HMS Pinafore". Most children would never have heard of "HMS Pinafore". "The Simpsons" is loaded with stuff that most children would not have a hope of getting.
It was really only with the emergence of television in the 1950s that most cartoons were made for children only.
See also -
http://www.cartoonbrew.com/classic/hollywood-censors-its-animated-cartoons-1939
http://blog.wired.com/tableofmalcontents/2007/03/the_hayes_offic.html