Random memory: knock-knock jokes and my father

I remember when I was a child, I used to like telling jokes, just as I still do.

And I'd often try to tell them to my father. Which was usually fine, but totally did not work with knock-knock jokes since he nearly always refused to coöperate.

A typical start would be "Knock, knock." -- "Come in!".

Occasionally, he could be a little coöperative and he'd ask "Who's there?", but when I reply with the setup, he'd say, "I don't know anybody called [setup]. Go away!" or something similar.

It was frustrating sometimes.