I saw Ben Folds on a TV special the other day and he talked about a lesson he learned from Vincent Price. Price said that you can’t have a truly scary horror movie unless it’s also a little bit funny. It’s the contrast that sells you on the fear.
Folds said he uses the same principle in his music, leavening the sad, serious stuff with the ridiculous and ironic. And, in addition to Folds, the group that jumps to mind when I think about that theory is Barenaked Ladies.