For anyone not convinced there's a fine line between comedic genius and outright insanity, I recommend MONTY PYTHON AND THE HOLY GRAIL.  The Python troupe takes the legend of King Arthur and mutates it into a hilarious kaleidescope of off-the-deep-end slapstick and parody.  Some of the humor is just plain silly (Black Knight:  "Come on and fight, you coward!"  Arthur:  "But I've just cut your leg off!"  Black Knight (pauses):  "It's only a flesh wound."), and we know it's silly, yet the viewer is still laughing uncontrollably.  Python can pull off looney tunes comedy like Olivier reciting Shakespeare; it's the reason the group enjoyed phenomenal success in the Seventies.