I've been flipping through Thomas Hoving's Master Pieces during my bored moments this week. (Hoving, now deceased, was the Met's director before Philippe de Montebello.) The book is a game Hoving played as a curator with other curators where someone would bring in details from paintings and everyone had to guess which paintings they were from.
And there's an entire section dedicated to butts.
Oh, Thomas Hoving. As if I wasn't already going to make my friends play this game when I get back to school.