Knock knock. Who's there? Dictionary.

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

Knock knock. Who's there? Donut.

Donut who? Donut ask, just open the door!

Knock knock. Who's there? Lettuce.

Lettuce who? Lettuce *pray* this joke *grows* on you, I've really *leafed* through a lot of ideas to *cultivate* this *gem* just for you, so please *romaine* here and enjoy!

Knock knock. Who's there? The unexpected.

The unexpected who? Exactly.