Combining a monster-of-the-week episode with a Scooby Doo crossover is easily the coolest thing Supernatural has ever pulled off. Dean, Sam, and Castiel getting zapped into an episode of the classic cartoon only to discover real ghosts are plaguing the Scooby gang leads to a funny and unforgettable animated hour. Oh, and let's not forget the perfection that is the Velma and Sam pairing, even though poor Sam is thoroughly confused by the whole event.