Knock knock. Who's there? Dwayne

Dwayne who? Dwayne the bathtub, I'm dwowning!

Knock knock. Who's there? Documentation.

who? This joke is still in beta and the punchline has not been implemented yet. Please try again later.

Knock knock. Who's there? Cows go.

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

Knock knock. Who's there? Wu

Wu who? Wu don't know, it's a Chinese puzzle to me, but I'm paws-itive I'll figure it out, fur-get about it!