Knock knock. Who's there? Wanda.

Wanda who? Wanda why you won't open the door!

Knock knock. Who's there? Dictionary.

Dictionary who? I'm not defining the terms of this conversation.

Knock knock. Who's there? Accordion.

Accordion who? Accordion to the weather report, it's going to rain!

Knock knock. Who's there? Cows go

Cows go who? No, cows go 'moo'