A man is sitting on the couch watching tv when his doorbell rings. He gets up and opens the door, but there is nobody there. Perplexed, he closes the door and sits back down to watch tv. About 5 hours later, the doorbell goes off again. He gets up to answer again, and this time finds a snail sitting on his porch. He throws the snail into his yard and closes the door.
Three years later, the man is on the couch watching tv when the doorbell rings again. He opens the door and finds the snail again. He picks up the snail, and the snail says "What the hell was that for?!"