Which supporting character does the best job of upstaging the hero?S

Every story needs a protagonist, who's noble and well-meaning and clever, and who struggles against darkness... freeing up the supporting cast to be just awesome and kick tons of ass. What's your favorite example of a supporting character who steals the hero's thunder?

Please include a picture or clip of this awesome character. And mention the name of the story that he/she comes from. Thanks!