I want to put a goofy figurine in someone's china cabinet!
I'd love to put a silly figurine amidst someone's fine china. Just standing there, next to a cup and saucer. Batman or some silly cartoon character. Perfect timing too, since the holidays are right around the corner.
Sort of like when Jerry put the Pez dispenser on Elaine's leg at the piano recital. It's not really funny in and of itself, just the inappropriateness of the item and the time/place make it funny.
Or, just poop in the punchbowl. That'll teach those stuck up bastards a lesson.