Knock, knock.
Who's there?
Who.
Who who?
You sound like an owl.
Who Sounds Like an Owl
Explanation
Explain Bear
Listen up, buttercup. This joke is a play on words. The person at the door says "Who," and the joke teller repeats it twice, making it sound like an owl hooting. It's funny because you expect a name, not an animal sound. It's funny AND stupid - just like the author of this joke (that's you).