Knock, Knock?

Who's there?
Nobody?
Nobody who?
Silence.......
Oh! I get it!

That was a joke from the movie "The Pursuit of Happyness".
One day I told this joke to Kira and it went like this: I said Knock, Knock? She said Who's there?, I said nobody, and she said "Then who knocked on the door?" I couldn't stop laughing! She couldn't understand why someone would continue with such a stupid joke! She liked her ending better! She has such a practical sense of humor!