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

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.
- My husband is still scarred by that one.
- Watership Down was what traumatized me on seeing blood in cartoons. Cartoons and blood just...dont mix.

Do Saturday Night Live skits count?
The Ambiguously Gay Duo
- I'll allow it

cow and chicken
- One of the shows that taught me English. And Dexter's Lab taught me French.
  
  Omelette du fromage
  
  Dexter's Lab was dope shit. Deedee was such a a great antagonist
- Catdog is quite similar in terms of "aesthetics" and craziness.
- I worked for the company that made that. Crazy shit

Ren and Stimpy
Beavis and Butthead
- Love B&B, still traumatized by the Ghost Fart from R&S
- Here they aired it at night, when not much else was there to watch. In my teenage years I was always hoping for some kind of erotic scene, but I was only left with confusion and switched the channel.

Rocko’s Modern Life was a helluva ride
- 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.
  
  Just stare into Really Really Big Man's Nipples of the Future.
- Rock was a favorite of mine. The nude beach episode really stuck out to me.
  And his dog's name was Spunky, ffs.

For me it was probably The Head.
I really liked Duckman as well.
Also, the early Beavis and Butt-Head
True classics, haha.

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
- How did they react afterwards ..?
  
  I don't really remember, I was 2, but I'm told they kept pushing me down in the back seat. LOL.
- That was the maybe original. Always loved how the cops were actual pigs

Ren & Stimpy

In my mid-teens, after Saturday Night Live they showed Fantastic Planet on Night Flight. That was an experience.
- I watched that on acid... Wow what an experience. Highly recommend
  
  Check out Gandahar. Anyone who thinks Star Trek has the most messed up time travel plotlines needs to watch this.

I'm still not sure whether "Angela Anaconda" was real or a collective fever dream.
- "hey what if we made a cartoon entirely about the revenge fantasies of a 12 year old girl?"
  "Sounds great, make it papercraft too, just to make it extra unsettling"
  
  "How about everything is in color except the peoples skin."
  "Brilliant."
- Amazing show!

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.

The lord of the rings cartoon. I still don't know wtf it is.
- That's just Ralph Bakshi movies. Try Wizards for some real wtf.
  
  Wizards had the best ending of any movie I've seen to date. It just comes out of fucking nowhere.
  
  There's another animated Hobbit besides Bakshi, which isn't bad. Not scary though.

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.
- If you like weird old SF books, the guy who wrote TAS and Gargoyles (RIP J. Michael Reaves) did a space-noir called Darkworld Detective, it's pretty good. Obviously unrelated to Batman though.

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

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)
- looks like it was animated on an Amiga
  
  Yup it was made on a Amiga 2000

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.
- Even the DVD menu for the Super Mario Brothers: Super Show was amusingly weird
  
  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.

The original sonic cartoon is like a chili dog induced fever dream
- You mean Adventures of Sonic the Hedgehog? I love Robotnik in that show!
  
  Yeah that's the one, with the surreal desert backgrounds like krazy kat comics
- Will check out

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
- i loved that. should do a whole series through calculus.
- What was the message it was trying to propagate?
  
  I think they were just trying to promote math. I always thought about it later in life as I tried to drunkenly calculate pool angles at the bar.
  "Dammit - Donald tried to explain this when I was 10! Why can't I remember the details?"

Can't believe no one has said it... Looney tunes.
- You have a point. In this thread, we're biased towards relatively more obscure cartoons, yet Looney Tunes practically invented the hyperactive uber-crazy cartoon.

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.
- Iznogoud maybe..?
  
  Yeah, that art style looks very familiar. I'll have to look into it more, since I'm starting to doubt some of the other details I provided. Oh, and the wiki says the animated series started airing on Canal+ in 1996. Maybe it aired elsewhere before?
  But yeah, I think this is it 👍.
  P.S. Iznogoud, like "is no good". I must have misremembered his name, cuz that makes sense!

The Last Unicorn

Did anyone watch Liquid Television?

The crazy stuff on Liquid Television
- Aeon Flux is still super weird 30 years later

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.
- Not sure on your first one, but the second was Cartoon All Stars to the Rescue

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

Was Attack of the Killer Tomatoes real or did I dream that?
- A series of movies & a Saturday morning cartoon show.
  Either it's real or we're both from the same alternate universe.
  
  Where there's a cornucopia in the fruit of the loom logo.

The Last Unicorn. Runner up, The Rats of Nymn.
- The Secret of Nimh is one of my favorite movies.
  
  I thought that was "The Secret of Nickel Metal Hydride" for the longest time.

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.
- OH MY GOD! I used to LOVE this as a kid, and recently remembered it. Nobody knows this amazing work.

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/
- What do you think of Veggie Tales? Actually wasnt mad imo
  
  I think I was older when it came out so I thought it was lame, pushing annoying.

TV series:
Oggy and the Cockroaches
Johnny Test
Teen Titans Go
Uncle Grandpa
The Amazing World of Gumball
Regular Show
Movies:
Coraline
Corpse Bride
Web series:
SMG4
asdfmovie

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.
- I'm so glad all this shit got greenlighted tho, tv in the 90's was wild, especially for kidz

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.

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

I was 12 and just getting into Anime, fresh off seeing Akira and Ninja scroll and hungry for more, I was not ready for Wicked City.
https://en.wikipedia.org/wiki/Wicked_City_(1987_film)

Watership Down.

“The great mouse detective” had a fight scene at the end that freaked me out as a kid.

Grave of fireflies

Vacalactica: https://www.youtube.com/watch?v=lF7tKWzkzi4

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.

Bible Black.
- that's just porn
  
  cartoon porn is still a cartoon.

I think for me it was Robot Chicken that would play late at night
- I have no idea when I first saw it but I loved it right away! I definitely loved it when Family guy would do anything claymation or with action figures like Dwayne Johnson showing Peter and Lois "having sex"

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.

Invader Zim

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.
- You mean from the Disney Little Mermaid movie?
  
  Yup, that's the one.

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.
- Tamest Chinese fantasy.
  
  Compared to other Chinese donghua I've seen in the past, the show definitely feels a little more unhinged. Most things I see today are a lot more average, in my opinion.

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.

It’s a very generational question. Like, many of the cartoons I watched as a kid would definitely be considered crazy today (and racist, misogynistic, murderous, etc.) but at the time were typical.

Bible Black and Gantz
- Gantz eh? Ok, I'll add Elfen Leid.
  
  That show blew. Senseless violence, I love violence with meaning.

Zap Comix #3
- Hey check out Mineshaft Magazine. Crumb is currently submitting work to them and they also regularly publish work from a few of those old Comix guys like Glenn Head, Hal Robbins, Kim Deitch, and Robert Armstrong, etc. They release about 2 per year.
  
  Sweet, thanks for the info.

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

Captain Condom

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