Prank Wars
From Super-wiki
Sam: Man, we’re not kids anymore, Dean. We’re not gonna start that crap up again.
Dean: Start what up? Sam: That prank stuff—it’s stupid, and it always escalates. Dean: Oh, what’s the matter, Sammy, you afraid you’re gonna get a little Nair in your shampoo again, huh?
Sam: All right. Just remember, you started it.– , 1.17 Hell House
Supernatural has a great tradition of pranks both on the Show, and behind the scenes.
