What separates Animaniacs from South Park, Beavis + Butthead, etc.
Animaniacs actually is not all that different from shows like South Park, Beavis & Butt-head, etc. Like those two shows, Animaniacs had a lot of adult oriented humor and cartoon violence. Animaniacs also pushed the envelope a bit in terms of what is acceptable to show in a cartoon.
However, unlike South Park and Beavis & Butt-Head, somehow, Animaniacs never really resorted to low-brow toilet humor. There was definitely toilet humor in Animaniacs, but somehow, the material was seldom disgusting as to offend parents. Parents still can feel comfortable having their kids watch Animaniacs, yet the parents themselves can enjoy the adult humor.
The adult humor in Animaniacs is a lot more subtle and clever. I think that's why this show has so much more appeal than the likes of Beavis & Butt-Head and South Park. Yes, Animaniacs has its share of raunchy moments, but it never goes so far as to gross the viewer out. Animaniacs somehow manages to be both a fun children's cartoon with clever adult humor that grown ups can enjoy. It's literally a show the whole family can enjoy, unlike South Park and Beavis & Butt-Head.