Knock knock. Who's there? Cash. Cash who? Yes! I've always known you were a bit nutty!
Knock knock. Who's there? Kenya. Kenya who? Keeeenya feeel the loooove tonight?
Knock knock. Who's there? FBI. FB… We are asking the questions here!
Knock, knock! Who's there? Opportunity! That is impossible. Opportunity doesn't come knocking twice!
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? Sarah. Sarah who? Sarah problem here?
Fan: "I see you won a silver medal at the Olympics. What's it for?¨" Athlete: "It's for telling knock knock jokes." Fan: "And what's that gold medal for?" Athlete: "For stopping."
Knock Knock. Who's There? Justin. Justin who? Your justin time to wipe my ass!
Chuck Norris was once part of a knock knock joke. The Joke ended abruptly when after the first knock the door blew up killing the man behind it.
Knock, Knock! Who's there? Doctor Doctor who? That's a great TV show, isn't it?