A knock knock joke goes like this:
A: Knock Knock
B: who's there?
A: <some name>
B: <some name> who?
A: <some joke or pun relating to the sound or meaning of some name>
B: <a groan or other indication that B didn't think it was funny>
For Example:
Knock Knock. Whos There?.
Boo! Boo who?
It's all right, please don't cry.
Knock Knock. Who's There?.
Banana! Banana who?
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 ya glad I didn't say Banana?
Knock, knock
Who's there?Orson
Orson who?Orson Buggy!
Knock, knock
Who's thereSam and Janet
Sam and Janet who?Sam and Janet evening, you will meet a stranger.... Ok... someone explain this one to me.... Oh and I ought to let you know that my sense of humor is so bad, I've put comedians out of business.
From South Pacific, the musical: Some enchanted evening, you will meet a stranger...
Knock Knock
Who's There?Doorbell Repair Service
<Knock Knock> Who's there? Avon Calling, Doorbell's broken.
The "JEDR" KnockKnockJoke:
"You start."
"Okay. Knock-knock."
"Who's there?"
"Um ... Um ..."
[on "JEDR": Ancient rec.humor.funny parlance for joke ethnic/denomination/race, and certainly not the initials of one Jonathan Richmond, in response to whose legal action against the moderator of the group the term was invented.]
"Knock, Knock"
"Who's there?"
"Knock, Knock"
"Who's there?"
"Knock, Knock"
"Who's there?"
"Phillip Glass"
Knock, Knock: Whose there?
Meter
Meter who?
Meter down stairs.... You're late.
A knock-knock joke is a good example to use when one of your non-geek friends asks you what a "protocol" is. It has a standard initiation message, followed by a standard acceptance message, a send-and-echo, and a final message that ends the transaction.
Some of the more interesting knock-knock jokes are those where the protocol is violated, such as the banana/orange and Philip Glass jokes above.
Knock, knock.
Who's there?
Philip.
Philip who?
Philip the tub so I can take a bath.
Knock, Knock.
Who's there?
Dwayne.
Dwayne who?
Dwayne the bathtub, I'm dwowning.
Knock, Knock.
Who's there?
Amsterdam.
Amsterdam who?
Amsterdam tired of these infernal knock-knock jokes.
Knock Knock, "Who's there?", "Amos", "Amos who", "Amosquito bit me."
Knock Knock, "Who's there?", "Andy", "Andy who", "Andy bit me again!"
Knock, Knock.
Who's there?
Impatient cow.
Impatient co--
MOOO!!!
Immediately afterward, if in physical presence of victim:
Knock, Knock.
Who's there?
Interrupting Starfish.
Interrupti-
''[Throws splayed hand in face of victim]"
[Note that "interrupting" gives you more time to interrupt in, and makes it harder for those in on the joke to just say the response fast]
And after that, if in presence of physicist victim:
Knock, knock.
Who's there?
An interrupting coefficient of friction.
An interru--
MU!
Knock, Knock.
Who's there?
Lil' ol' lady
Lil' ol' lady who?
I didn't know you could yodel!
Here's a RudyGiuliani? knock knock joke:
Knock, Knock
Who's ther-
9/11!!
See LightBulbJoke, WorstPunEver