Knock knock. Who's there? Dictionary.

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

Knock knock. Who's there? Ivan.

Ivan who? Ivan telling you to open this door for ages, my knuckles are practically knocking themselves!

Knock knock. Who's there? Existential Crisis.

Existential Crisis who? I'm not really sure, because the concept of identity and self is fleeting and meaningless in an infinite universe.

Knock knock. Who's there? Next.

Next who? Next time, just open the door, this isn't a surprise party.