One day a man heard knocking at his door. He opened the door only to see a small snail sitting there smiling. The guy picked the snail up and threw it as far as he possibly could. Three years later he heard knocking at the door again. He opened the door to see the snail. The snail said, "What the hell was that all about?"
"Knock, knock.Who's there?" very long pause... "Java."
Knock Knock! Who's there? Zany Zany who? Zany body home?
Knock, Knock! Who's there? D umbbell. Dumbbell who? Dumbbell doesn't work so I had to knock!
Knock knock. Who's there? Cash. Cash who? Yes! I've always known you were a bit nutty!
Peter approaches the gates of Heaven. "Knock knock," says Peter. Miraculously, someone answers him. "Who's there," a voice in the distance asked. "God," says Peter. "God who," asked the voice? "GOD DAMMIT open these gates! I've been a good neighbor, loved my wife and lost my virginity, twice!"
Knock knock. Who's there? Urine. Urine who? Urine trouble if you don't open the door.
Knock knock. Who's there? Déja. Déja who? Knock knock.
Knock, knock! Who's there? Opportunity! That is impossible. Opportunity doesn't come knocking twice!
Knock-knock. Who's there? To. To who? No, to whom.