Use the adjective campy to describe something that has a ridiculous, wacky appeal. Some movies are so exaggeratedly bad that they've got a campy kind of charm.
Anything you describe as "so bad it's good" is probably campy. Many fans of over-the-top, campy films like "Rocky Horror Picture Show," for example, find them wonderfully funny and strange. The early twentieth century slang meaning of camp was simply "tasteless," with campy emerging in the late 1950's. The root is uncertain, but it may be the French se camper, "to put oneself in a bold, provocative pose."