Knock knock. Who's there? Tank.

Tank who? Tank you for opening the door!

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? Flake

Flake who? Snow-body's home.

Knock knock. Who's there? Dough.

Dough who? Dough-n't worry, I knead to come in.