The classic knock knock joke has so many hilarious variations, and they're all here.

Knock, knock.
Who's there?
Kenya
Kenya who?
Kenya guess who is it?
Knock, knock.
Who’s there?
Caesar.
Caesar who?
Caesar quick, she’s running away.
Knock, knock.
Who's there?
Ben
Ben who?
Ben knocking on this door all morning, let me in!
Knock, knock.
Who's there?
Harry.
Harry who?
Harry up, it’s cold out here!
Knock Knock
Who's there?
Mary
Mary who?
Mary Christmas!
Knock, knock.
Who’s there?
I am.
I am who?
You mean you don’t know who you are?
Knock, knock.
Who's there?
Bruce
Bruce who?
I Bruce easily, don't hit me!
Knock, knock.
Who's there?
Broccoli.
Broccoli who?
Broccoli doesn't have a last name, silly.
Knock, knock.
Who’s there?
Aida.
Aida who?
Aida sandwich for lunch today.
Knock, knock.
Who's there?
Cheese
Cheese who?
Cheese a nice girl.
Knock, knock.
Who’s there?
Nana.
Nana who?
Nana your business.
Knock, knock.
Who's there?
Les
Les who?
Les go out for a picnic!
Knock, knock.
Who’s There?
Imma.
Imma Who?
Imma gettin’ old open the door!
Knock, knock.
Who's there?
Control freak.
Co…
You should say "Control freak who" now.
Knock Knock!
Who’s there?
Yah.
Yah who?
No, I prefer Google.
Knock knock.
Who’s there?
Cantaloupe!
Cantaloupe who?
Cantaloupe to Vegas, our parents would get mad.
Knock Knock Jokes
Knock, knock.
Who’s there?
Canoe.
Canoe who?
Canoe help me with my homework?
Knock, knock.
Who’s there?
Abby.
Abby who?
Abby birthday to you!
Knock, knock,
Who’s there?
Olive.
Olive who?
Olive you!
Knock, knock
Who’s there?
Merry.
Merry who?
Merry Christmas!
Knock, knock.
Who's there?
Amish!
Amish who?
You're not a shoe!
Knock knock.
Who's there?
Toucan.
Toucan who?
Toucan play at that game!
Knock, knock.
Who's there?
Fork
Fork who?
Fork-get it, I'm leaving!
Knock, knock.
Who’s there?
Icy.
Icy who?
You see me, do you need glasses or something?
Knock, knock.
Who’s there?
interrupting doctor.
interr…
You've got cancer.
Knock Knock
Who's there?
Two 4's.
Two 4's who?
No need to make lunch we already 8.
Knock, knock.
Who’s there?
Justin.
Justin who?
Justin time for dinner.
Knock knock
Who's there?
To.
To who?
Surely you mean to whom.
Knock Knock.
Who's there?
Pasta!
Pasta who?
Italian chef who pasta away.
Knock, knock.
Who's there?
Lock
Lock who?
Lock who it is, after all this time!