Me: Knock, knock.
Other person: Who’s there?
Me: Atch.
Other person: Atch who?
Me: Bless you!
Atch Who?
Explanation
Explain Bear
Hey, listen up, buttercup. This joke works 'cause it sounds like "a chew" which is what you do when you sneeze. So instead of saying "Atch who?" the person is tricked into having to bless the sneezer! Bet your brain is still trying to process that, huh?