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

Knock Knock Jokes

Knock knock
Who's there?
To.
To who?
Surely you mean to whom.
Knock Knock
Who's there?
Spain!
Spain who?
Spain to have to keep knocking on this door!
Knock, knock.
Who’s there?
I am.
I am who?
You mean you don’t know who you are?
Knock, knock.
Who’s there?
Hoo.
Hoo who?
Are you an owl?
Knock, knock.
Who’s there?
Two knee.
Two knee who?
Two-knee fish!
Knock, knock
Who’s there?
Ben.
Ben who?
Ben knocking For 10 minutes.
Knock, knock.
Who’s there?
Police.
Police who?
Police hurry up, it’s chilly outside!
Knock, knock.
Who’s there?
Scold.
Scold who?
Scold enough out here to go ice skating.
Knock, knock.
Who’s there?
Iona.
Iona who?
Iona new car!
Knock, knock.
Who’s there?
Aida.
Aida who?
Aida sandwich for lunch today.
Knock, knock.
Who’s there?
Roach.
Roach who?
Roach you a letter, did you get it?
Knock, knock.
Who’s there?
Ya.
Ya who?
Wow. You sure are excited to see me!
Knock, knock.
Who’s there?
Nana.
Nana who?
Nana your business.
Knock, knock.
Who’s there?
Abby.
Abby who?
Abby birthday to you!
Knock, knock.
Who’s there?
Arfur.
Arfur who?
Arfur got!
Knock, knock.
Who’s there?
Ivor.
Ivor who?
Ivor you let me in or I`ll climb through the window.
Will you remember me in a minute?
Yes.
Will you remember me in a week?
Yes.
Will you remember me in a year?
Yes.
Knock, knock.
Who’s there?
You didn’t remember me!
Knock, knock.
Who’s there?
Justin.
Justin who?
Justin time for dinner.
Knock, knock,
Who’s there?
Olive.
Olive who?
Olive you!
Knock, knock
Who’s there?
Sadie.
Sadie who?
Sadie magic word and watch me disappear!
Knock, knock
Who’s there?
A little old lady.
A little old lady who?
I didn’t know you could yodel.
Knock, knock.
Who’s There?
Impatient cow.
Impatient cow wh-?
Mooooo!
Knock, knock.
Who’s there?
Boo.
Boo who?
Gosh, don’t cry it’s just a knock knock joke.
Knock, knock.
Who’s there?
Banana.
Banana who?
Knock, knock.
Who’s there?
Banana.
Banana who?
Knock, knock.
Who’s there?
Orange.
Orange who?
ORANGE YOU GLAD I DIDN’T SAY BANANA!
Knock, knock.
Who’s There?
Imma.
Imma Who?
Imma gettin’ old open the door!
Knock, knock.
Who’s there?
Dwayne.
Dwayne who?
Dwayne the bathtub, It’s overflowing!
Knock, knock.
Who’s there?
Robin.
Robin who?
Robin the piggy bank again.
Knock, knock.
Who’s there?
Noah.
Noah who?
Noah good place we can get something to eat?
Knock, knock.
Who’s there?
King Tut.
King Tut who?
King Tut-key fried chicken!
Knock, knock.
Who’s there?
Otto.
Otto who?
Otto know. I’ve got amnesia.