What was the craziest cartoon(s) you saw whilst a kid?

Danger Mouse - I think the consistent 4th wall breaking, kidnapping narrators, and sense of humour as a whole had an effect on my from a formative age.

Monkey Dust - the cartoon that made it clear to me that cartoons weren't not at all nesseccarily safe for kids. I was too young to appreciate it at the time, it was too disturbing for tween me.

Sealab 2021 and Excel Saga both crazy animations that I found easier to digest about that time, too.

Watership Down, other folks have already mentioned.

I think for me it was Robot Chicken that would play late at night

Grave of fireflies

Can't believe no one has said it... Looney tunes.

Did anyone watch Liquid Television?

Invader Zim

If we're counting highschool as still a kid, the old Chinese cartoon Calabash Brothers. Still looking for ENG subs for the newer version that released in the 2010s, though.

It's a cartoon where a snake and scorpion demon escape from a mountain and an elderly man has to grow a magic calabash seed that turns into 7 different calabashes that turn into little dieties when ripe in order to stop the demons.

Ren & Stimpy

I thing Dutch people from my generation have you all beat:

Purno de Purno (porn pun very much intended)

A psychedelic cartoon about a funny guy in spandex that has a shitload of nudity (tits, penisses etc) to the point of him even crawling in the vagina of a giant lady in space. It has references to litaral drug use. Have a look here: https://www.youtube.com/watch?v=4o6MIJ7Iq1U doesn't matter if you know the language, just browse through. That episode is called 'In het hol van de kietelaar' which translates to 'In the clitoris' hole'

This was on kids tv. Nobody got seriously harmed by it. It was funny and weird, but you don't really register exactltyy how weird it is untill you hear about sensitivities on US TV (nipplegate lol)

a stll, much more to find

Well there's many mentions so I'll add one I have yet to see listed, The Adventures of Mark Twain is always an unsettling classic.

For me it was probably The Head.

I really liked Duckman as well.

Also, the early Beavis and Butt-Head

True classics, haha.

Gantz, Watership Down, Animal Farm, Super Jail, and Urslua looks like my father's mother, whom I hated, so I freaked the fuck out when my mom brought that VHS he.

The oblongs, ripping friends, Ren n Stimpy, I r baboon were some of the best. Drawn together was a gem too that came out when i was a teen

Rocko’s Modern Life was a helluva ride

Bible Black.

Pretty much any British children's animation from the seventies.

Duckman, though that was not for kids.

Ren and Stimpy and Rocko's Modern Life both had stuff that was bizarre and only allowed in a kid's show because it was over their heads.

Batman TAS and Gargoyles both had some heavy shit. The latter also had a guy die by having fire erupt from behind his eyeballs, and a scene where a surgeon explains a gunshot wound in visceral detail. God I love that show.

cow and chicken

Watership Down.

Was visiting relatives and we rented movies from a tiny video store that didn't have a lot of options or kids, so we got that and Crocodile Dundee.

Dundee was fun. The bunnies were less so.

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.

Ren and Stimpy

Beavis and Butthead

Do Saturday Night Live skits count?

The Ambiguously Gay Duo

Bible Black and Gantz

I'm still not sure whether "Angela Anaconda" was real or a collective fever dream.

Was Attack of the Killer Tomatoes real or did I dream that?

The original sonic cartoon is like a chili dog induced fever dream

When I was like, 2? My parents were like "Hey! What's this new cartoon? Let's take the kid to the drive-in!"

Fritz the Cat:

https://youtu.be/T34GGPaPnrk

The Last Unicorn. Runner up, The Rats of Nymn.

In my mid-teens, after Saturday Night Live they showed Fantastic Planet on Night Flight. That was an experience.

The Brave Little Toaster. It's a bit endearing until the LSD trip goes bad.

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.

The crazy stuff on Liquid Television

The lord of the rings cartoon. I still don't know wtf it is.

Muran Buschstansangur

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.

If anyone knows anything about this cartoon, LMK.

The Last Unicorn

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.

The most hauntingly memorable was a weird mid-century Donald Duck piece of math propaganda. We watched it in school.

Donald Duck in MathMagic Land. Not scary, but odd.

https://www.youtube.com/watch?v=8BqnN72OlqA

Adolar's Fantastical Adventures

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.

Ugh Probably Teens Titans GO: Its episodes just go from Fart Jokes to how to pay Taxes.

Quads was fucking wild. I remember watching it in between Undergrads and the Oblongs. The wonders of having both parents work night shifts.

Watership Down.

I saw a lot of Christian propaganda cartoons.

I remember there was a whole series where kids traveled through time to watch "historical" events.

https://www.imdb.com/title/tt5090166/

The Point!

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]

I’m pretty sure this is why I do drugs today.

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.

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.