The first thing which comes to my mind is – A must-do prank! 😛

A Pythagorean Cup OR a Greedy Cup is a form of a drinking cup which forces its user to consume less alcohol. It allows the user to fill the cup with wine, alcohol or any other liquid up to a certain level. If the user fills only up to this level, one can enjoy his drink in peace.
But if one adds more of it by filling it more than a certain limit, the cup spills its entire content out of the bottom (onto the lap of a greedy drinker). more “Pythagorean Cup – The clever mischievous cup !”