Knock knock. Who's there? Dictionary.

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

Knock knock. Who's there? Disguise.

Disguise who? The sky's the limit for wordplay, so prepare for an un-pun-believable groan-fest!

Knock knock. Who's there? It's me, Kevin. We talked about this. I'm here for the pizza.

It's me, Kevin. We talked about this. I'm here for the pizza who? Seriously, it's just Kevin. You ordered a pepperoni, right?

Knock knock. Who's there? Egg

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