I was reminded of Heavy Metal (1981) by a very dumb movie podcast. Of course, I remembered the movie well - I saw it in the theater and more recently on CD. But I had forgotten, or never knew, that John Candy, Joe Flaherty, and Eugene Levy had done some of the voices. So we had to watch again with this knowledge.
If you don't know, this is the movie based on the adult comic magazine of the same name. It is basically a series of animated shorts, tied loosely together by the tale of a malignant glowing meteor. Heavy breasted nude women are heavily featured. There's a lot of heavy rock on the soundtrack, although the metal is a bit on the light side (Grand Funk Railroad, Sammy Hagar, Blue Oyster Cult. Cheap Trick?). The animation styles are varied, with a lot of rotoscoping. The biggest influence is the French artist Moebius. I remember hoping that the movie was going to tackle Jerry Cornelius' Airtight Garage, a classic Moebius strip, and being disappointed because there was so little Moebius influence overall. I can see now it was more subtle, but it's there.
And as for Candy et al.: they don't really stand out. The exception is the Den section. It's about a geeky Earth teen who is magically transported to a barbaric land, where he is a huge, muscular, bald dude. He fights the evil (large breasted, nude) priestess and rescues the ritual sacrifice (also large breasted and nude). It's a good story, but having Candy narrate in his squeaky geek voice really made it special.
In conclusion, the movie is about as good as I remembered it: fun, not 100% great. Decent music, including the score by Elmer Bernstein, but could have been better. Knowing that the SCTV guys were doing voices was interesting, but not really crucial.
Produced by Ivan Reitman (Ghostbusters, etc), which probably explains a lot.