Knock knock. Who's there? Fig.

Fig who? Fig-ure it out yourself!

Knock knock. Who's there? Cows go.

Cows go who? No, cows go 'moo'.

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? Just me.

Just me who? What do you mean 'who'? I'm the person standing right here!