In the 1990s, the Simpsons brought animation back to primetime and right on the Simpsons' heels, Ren and Stimpy changed everything. Ren and Stimpy might have run on a kids' network (Nicholodeon) but it was aimed at teens and young adults. It was crass and surreal -- everything the early Avery and Feisher cartoons had but with a big dose of toilet humour. At the time, it was too crass for me but now it looks positively tame.
Most of the cartoons that run in the Adult Swim timeslot on the Cartoon Network (and on Detour, the Canadian equivalent) owe a lot to Ren and Stimpy -- everything from Robot Chicken (which also owes a debt to SNL and Kids in the Hall) to Aqua Teen Hunger Force.
If spend any time with me, you know I am a sucker for animated shows, cartoons and movies. I hope I never outgrow that.
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Classic Betty Boop animation from the Internet Archive:
Ren and Stimpy episode via Youtube:
Controversy over the Aqua Teen Hunger Force movie: