Knock knock. Who's there? Taco.

Taco who? Taco 'bout a good time!

Knock knock. Who's there? Parenthesis.

Knock knock. Who's there? Cows go.

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

Knock knock. Who's there? Nimbus.

Nimbus who? Nimbus sure I'm at the right door, the forecast said I'd find you here!