At the time I just remember everyone saying it was trash and comparing it to Ultraviolet. Little discussion of the animation it was based on, which doesn’t seem that popular. It does have a cult following, though.
I’ll nominate the Gideon Cartoons. I saw them years ago on Calliope on USA network. They didn’t seem that weird back them, but now when I watch them they are creepy/trippy/weird.
I really like the music though.
Pfft. The Maxx? Aeon Flux? Those weren’t weird. Don Hertzfeld’s stuff is awesome; Billy’s Balloon is one of the funniest cartoons ever made.
I’m starting to think that most of you never get outside the mainstream… or should I say [Palin voice] ‘lamestream’ [/Palin voice] ? 
Now Paper Rad (this is just a short clip of some of their work) is some fucked up shit. Their Trash Talking DVD is an incomprehensible, seizure inducing hour of bizarre and unlikely creatures doing incomprehensibly bizarre things. The art is crazy. The sound is crazy. I have no idea what some of the characters are supposed to be or what they are doing. It’s like watching something created by schizophrenics who had taken massive doses of LSD and who had never seen a cartoon before in their lives. It is one of the most maddening things I know of to watch after ingesting hallucinogens.
Of course, I am proud to own it! 
Also, an honorable mention should go to anything by cyriak; check out Baaa.
ETA: For semi-mainstream weirdness, I’ll put my money on Aqua Teen Hunger Force.
A lot of anime look like they are super-weird, especially if you just read a short premise. In practice most of them may have a weird premise but are totally cliche once they get going: the same old moe-blob girls colliding with spineless and bland male mains, falling down in a heap so that the boy grabs their boobs or whatever. There’s some weird ones in the mix but they are a tiny minority IMO.
Ub Iwerks cartoons. “Balloon Land” (1935) is one of the worst, a horrible phallic nightmare. The PIN CUSHION MAN will POP YOUR CHERRY.
Invader Zim and Courage the Cowardly Dog are pretty damn strange for mainstream toons too.
I’ve always been partial to Koko’s Earth Control. Music by Paul Whiteman and his Orchestra.
Pink Floyd had some trippy animations for The Wall. Those flowers, man.
Son of a Rich, old cartoons are crazy.
Snowboarder Bo, that was pretty weird. I was thinking of works with some sort of story. There’s all sorts of batshit stuff on the internet, ranging from flash animation to YTPs (Fawful’s stuff is pure art). Then again, a lot of Firth’s standalone vids don’t make any sense either.
The Maxx has a subreddit with like 50 subs. Aeon Flux doesn’t even have one. Don’t think they’re that mainstream, or maybe it’s just not fresh enough for the kids nowadays. I don’t know if they could even air some Flux episodes today, what with all the BDSM and freaky tongue kissing scenes. Or that episode where Trevor fingers a woman’s spinal cord hole.
Oh, there’s a story being told in Paper Rad’s Trash Talking; it’s just incomprehensible. Seriously. I’ve watched that damn thing 3 times completely sober and at least 4 times when completely not-sober, and I have no idea what’s going on or why or who anyone is.
Paper Rad also did a show that aired on Cartoon Network for 2 years called The Problem Solverz. Check out the premiere episode, Time Twister. It’s at least semi-coherent, but still just whacked out of it’s gourd.
They also did a Super Mario “movie” (it’s only 15 minutes long) back in 2005 that is completely fucked up.
Watching the color Betty Boop cartoons is like going on a drug trip.
Korgoth the Barbarian is awesomely weird.
Spinnolio twisted takeoff on Pinocchio.
https://www.youtube.com/watch?v=1ieTlexV2SQ
Adult Swim has a pretty good record for semi-mainstream weirdness, in addition to Aqua Teen Hunger Force; one show that comes immediately to mind is the 20 episodes of Xavier: Renegade Angel. It offers bizarre plots, bizarre dialogue, and bizarre graphics.
I remember seeing some of the early Max Fleischer stuff. It was I believe early 1930’s and somewhat experimental animation. I don’t think LSD was available then, but he must of been on something heavy. Wiki describes it as “sophisticated, focused on surrealism, dark humor, adult psychological elements, and sexuality.”
And for-what-it’s-worth, Betty Boop was originally a dog. No, no, not commenting on her looks, but a true cartoon dog.
I will second Fantastic Planet and some of what was on Liquid Television.
Maybe psilocybin mushrooms in the bootleg liquor?
BIMBO’S INITIATION (1931) is a good introduction, and Betty-as-dog makes an appearance at the very end.
(Also, LSD was created in the early 1940s)
Bats in the Belfry, by Rudolf Ising, had me scratching my head when I watched it many years ago. I was reminded of it by this thread, so I just watched it again.
Yep, still weird.
I’ll see your “Bimbo’s Initiation” and raise you “Swing You Singers!”
Oh, yeah, and there’s the seriously disturbing Booboo Runs Wild, by John Kricfalusi.
When my daughter was little, we rented this from the library, it was on a double bill with George Pal’s Tubby the Tuba short (from 1947). For some reason, both scared the bejesus out of my kid. I thought it was some no-name cheapie thing, and I watched and was just mesmerized. Both WERE creepy as F in an otherworldly way.:eek: