Knock knock. Who's there? Existential Crisis.

Existential Crisis who? I'm not sure, I've been questioning the meaning of my own existence and the nature of identity, so the concept of a 'who' is somewhat fluid to me.

Knock knock. Who's there? Wire.

Wire who? Wire you not opening the door?

Knock knock. Who's there? Wheat.

Wheat who? Wheat you waiting for, let me in, it's a-maize-ing!

Knock knock. Who's there? Dictionary.

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