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

Knock, knock.
Who’s there?
Iva.
Iva who?
I’ve a sore hand from knocking!
Knock knock
Who's there?
To.
To who?
Surely you mean to whom.
Knock, knock.
Who's there?
Lego
Lego who?
Lego of me and I'll tell you!
Knock Knock
Who's there?
Centipede.
Centipede who?
Centipede on the Christmas tree.
Knock, knock.
Who's there?
Amanda
Amanda who?
A man da fix your sink!
Knock, knock.
Who's there?
Etch.
Etch who?
Bless you.
Knock, knock,
Who’s there?
Olive.
Olive who?
Olive you!
Knock knock.
Who’s there?
Cantaloupe!
Cantaloupe who?
Cantaloupe to Vegas, our parents would get mad.
Knock Knock
Who's there?
Ireland!
Ireland who?
Ireland you money, if you promise to pay me back.
Knock Knock Jokes
Knock, knock.
Who’s there?
Canoe.
Canoe who?
Canoe help me with my homework?
Knock, knock.
Who’s there?
Irish.
Irish who?
Irish you a nice day.
Knock, knock.
Who's there?
Ken.
Ken who?
Ken I come in?
Knock Knock!
Who's there?
Honeybee.
Honeybee who?
Honeybee a dear and open the door, please.
Knock, knock.
Who's there?
Lock
Lock who?
Lock who it is, after all this time!
Knock knock.
Who’s there?
Mustache.
Mustache who?
Mustache you a question, but I’ll shave it for later
Knock knock.
Who’s there?
Police.
Police who?
Police stop telling these awful knock-knock jokes!
Knock, knock.
Who’s there?
Ivor.
Ivor who?
Ivor you let me in or I`ll climb through the window.
Knock, knock.
Who’s there?
Dwayne.
Dwayne who?
Dwayne the bathtub, It’s overflowing!
Knock Knock Who's there?
Pecan!
Pecan who?
Pecan somebody your own size!
Knock Knock
Who's there?
Anna!
Anna who?
Anna partridge in a pear tree.
Knock knock.
Who's there?
Beats.
Beats who?
Beats me.
Knock, knock.
Who’s there?
Abby.
Abby who?
Abby birthday to you!
Knock, knock.
Who's there?
Double
Double who?
W!
Knock Knock
Who's there?
Snow
Snow who?
Snow business like show business!
Knock, knock.
Who's there?
Jester
Jester who?
Jester silly old man!
Knock Knock
Who's there?
Holly
Holly who?
Holly-days are here again!
Knock Knock.
Who's there?
Pasta!
Pasta who?
Italian chef who pasta away.
Knock, knock.
Who’s there?
Hoo.
Hoo who?
Are you an owl?
Knock, knock.
Who's there?
Ice cream!
Ice cream who?
Ice cream if you don't let me in!
Knock Knock!
Who's there?
Rabbit.
Rabbit who?
Rabbit up carefully, it's a present!