Knock knock. Who's there? A philosophical question.

A philosophical question who? If a joke falls flat in the forest, and no one laughs, was it ever funny?

Knock knock. Who's there? Cows go.

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

Knock knock. Who's there? Philosophically speaking, the notion of a 'who' is a social construct and the concept of identity is fluid, so the idea of a fixed entity on the other side of the door is a fallacy.

Knock knock. Who's there? A man with a

manuscript for a knock-knock joke, but he's struggling to come up with a decent punchline, and honestly, it's just getting a bit meta at this point.