Knock Knock! Who's there? Zany Zany who? Zany body home?
Knock Knock! Who's There? Figs Figs who? Figs the doorbell, it's broken!
Knock Knock! Who's there? Justin Justin who? Justin time for dinner!
Knock, Knock! Who's there? Doctor Doctor who? That's a great TV show, isn't it?
Knock-knock Who is there? A shattered penis with many diseases. What kind of illness? Gall, Aids, Gonorrhea, Syphilis... Enough, it is the best present for my mother in law.
Knock Knock. Who's there? Opportunity. Don't be silly - opportunity doesn't knock twice!
Knock knock. Who's there? Urine. Urine who? Urine trouble if you don't open the door.
Knock knock! Who's there? Yah! Yah who? Naaah, bro, I prefer google.
"Knock, knock.Who's there?" very long pause... "Java."
"Mommy, mommy, I found daddy!" "How often do I have to tell you not to dig around in the garden!"
Q. What did the porcupine say to the cactus? A. "Is that you mommy?"