The
Wikipedia article on it does nicely to describe it.
I can see it going over some heads - it's ridiculously bizarre, and often cruel to various pieces of Japanese pop culture. But its humor rests more in non sequiturs and absurdities more than just plain mockery.
The eponymous hero is a funky dresser in a blond afro who fights with his nose hairs. His brain and nasal cavities seem to contain myriads of creatures that reveal his thoughts or help fight his battles. He fights mixed-up weirdos and go on odd quests. Recently I saw him being pulled along on a cart as he spent a week in a hamburger bun to see how it feels to be said item (he's a vegetarian).
It's friggin' nuts without being self-absorbed and self-referential in its wackiness (like
12 Oz. Mouse or
Sealab 2021 or
Family Guy). It's just insane.