Knock knock. Who's there? Olive.

Olive who? Olive this conversation, it's going nowhere!

Knock knock. Who's there? Wu

Wu who? Wu don't know, I'm having an identity crisis!

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? Egg

Egg who? Egg-cuse me, I'm cracking under the pressure to make a good pun.