I was a kid in the 90's. It'd probably be easier to list the normalest cartoons. Like Doug.
Freakazoid, possibly. Or Toxic Avenger. Though the latter is more insane that they turned the original concept into something for kids in the first place.
I was amazed at the shit they were allowed to play in the after school block on Nick/CN sometimes. Rocco might take the cake with the masterbation milking episode
It wasn't originally designed for kids, and it really shows with the pilot episode. It had swearing in it and most of the jokes would go over kids' heads. Certainly went over mine until I re-watched it as an adult.
The first one that comes to mind is this one from probably the early 90s. From what I remember it was a group of kids and one of them is sick or something and the other kids try to save him? In the end they each sacrifice a year of their life so that the sick friend can live. I wanna say Steven Spielberg was a producer.
There was also that one crossover movie where a bunch of cartoon characters from whatever was popular in the 80s did an anti-drug movie.
Oh, man, when I was a kid around 1990 I was in France (maybe? Pretty sure it was somewhere in Europe), and they had this subtitled cartoon (I didn't know either language) that "starred" a villain named something like Amin Tumani ("I'm in to money", but made into a name) that was a stereotypical middle easterner. And to add to the crazy I'm 99.9% sure he died at the end of every episode.
An old Hungarian cartoon about a boy who hides an inflatable rocket in his violin case. He uses it to fly to strange planets like a two dimensional one. Most vivid image I have in my mind is how the rocket stretches when it approaches light speed.
The old Nintendo cartoons, things like the Mario Super Show and the classic Sonic show. If you thought live action Mario and Luigi arguing with fungus people was weird, sometimes the people behind the cartoons would get so lazy that they wouldn't fully draw some of the frames or throw in a lazy scenario for the main characters like "what if Yoshi had a secret family he was hiding off-screen". Of note, people often ask me "why are you so relatively soft on the Zelda CDi games" and the answer relates to the deal of effort.
If puppet shows count, objectively it's Mr. Meaty.
That moment when Shigeru Miyamoto made Mario because he couldn't get the rights to Popeye, yet DiC has the power to make Inspector Gadget a part of Mario canon. Chad move.
From Wikipedia:
The Point! is a fable that tells the story of a boy named Oblio, the only round-headed person in the Pointed Village, where by law everyone and everything must have a point. Nilsson explained his inspiration for The Point!:
"I was on acid and I looked at the trees and I realized that they all came to points, and the little branches came to points, and the houses [each] came to [a] point. I thought, 'Oh! Everything has a point, and if it doesn't, then there's [still] a point to it.'"[4]
Mid-90s, I used to stay up all night long on Fridays, watching weird cable access shows and infomercials. There was a Highlander: The Animated Series cartoon that came on around 4AM. No one ever believed me when I tried to describe it.
Probably the Toxic Crusaders, but only after watching the movie it's based on.
The cartoon itself is just another knockoff TMNT, which was the style at the time. I have no idea how someone showed a board of directors the Toxic Avenger in the early 90s and said, we should take this and make it a cartoon for children.