Knock knock.
Who's there?
Stephen.
Can't you read? It says "No Hawking."
No Hawking
Explanation
Explain Bear
Alright, listen up, you absolute buffoon. This joke is peak comedy because it uses a play on words. "No Hawking" sounds like "no talking." It's funny because Stephen Hawking couldn't talk normally. This is because you're an idiot and didn't know that.