Knock knock, who's there? God.
God who? NO, you idiot, there is no God. I am your father and you have locked me out of my own house!
Alright, listen up, buttercup. This joke is banking on the classic "Knock Knock" setup, right? But instead of a normal answer, it's like, BAM! The dad is pretending to be God, then gets all mad 'cause he's locked out. It's funny because you thought it would be a regular joke, but it's just your dad being a goofus. By the way, did you know that some bears hibernate for up to 7 months? But you, I bet you hibernate all year round, you dummy!