Another movie question, but this may be the WORST movie ever!

One late night after work (about 4am), I caught the middle of an old sci-fi movie. The style was similar to Flash Gordon , but somehow older looking. The “scientists” stumbled around above ground on hummocks or hills that were clearly modeled after breasts and then somehow wound up below ground interacting with a race of beings made up of poo (actors actually wearing poo costumes). Everytime I try to describe this movie to anyone, they accuse me of recreational drug use. Can anyone help me with identifying this classic bit if cinema?