Knock knock. Who's there? Next question.

Next question who? Next question... oh, this isn't an interview!

Knock knock. Who's there? The premise.

The premise who? The premise for a knock-knock joke needs two people, and I'm talking to myself.

Knock knock. Who's there? Existential Crisis.

Existential Crisis who? I'm not really sure, because the concept of identity and self is fleeting and meaningless in an infinite universe.

Knock knock. Who's there? Cows go.

Cows go who? No, cows go 'moo'.