Well, there was that one episode of Spongebob- "Procrastination" You know the one, where he had to write an 800-word essay on what not to do at a stoplight. It was mostly the dream sequence near the end...
...actually, most dream sequences in cartoons can tend to be creepy/weird, most of the time.
Other shows that fall under the "oh my god what the heck am I watching" category were Courage the Cowardly Dog, Invader Zim, and Rocko's Modern Life- Coincidentally, all shows that I loved back then, and still love even now...though, I must admit to Rocko's Modern Life being more entertaining to an older audience, apparently...All those jokes I must've missed. Animaniacs, too, but that's a discussion for another topic...
Ren and Stimpy is another weirdly creepy show, but I've seen it more recently than "childhood", so I'm not sure if it counts...well, except for the Black Hole episode, though I've only recently remembered watching it back then...guess I supressed it from my memory, or something.
