Knock knock. Who's there? Existential Crisis.

Existential Crisis who? I'm not sure, but the meaninglessness of this joke is a reflection of the void that lies at the heart of our existence.

Knock knock. Who's there? Wanda.

Wanda who? Wanda why you won't open the door!

Knock knock. Who's there? Anita.

Anita who? Anita little help with these heavy bags!

Knock knock. Who's there? Mango.

Mango who? Mango-nificent to meet you!