I have, in one of my tenth-grade classes, a boy whose voice sounds exactly like Marvin the Martian, minus the British accent. When he first talked today, I had to lean over to the real teacher and ask her if that's his real voice. It's fantastic, but it's also rather hard to resist the urge to giggle and teach him phrases like "Oh goody! My Illudium PU-36 Explosive Space Modulator."
(Surely there must be some situation that phrase could come in handy...)