Knock knock jokes

Today I told my Polish co-worker Piotrek the "Impatient Cow" knock knock joke. He laughed uproriously. It was great. I had never seen that kind of response to a Knock Knock joke.

Then he told me the "Mary Christmas" knock knock joke, but he could barely get through it without laughing.

Lenka couldn't quite grasp the format of the Knock Knock joke. But that is not her fault. The only ones I could think of were "Impatient Cow" and "Orange you glad I didn't say "banana?", both of which are more advanced. She kept saying "WHO banana???" And answering my "banana" by with "banana."

I can't wait to try more jokes on Piotrek. If you find any good ones, please send them my way.