because some people forget the joke and/or tell it wrong
This is a variety of knock-knock joke where the person telling the joke keeps interrupting whenever the other person tries to ask what the interrupting cow actually says.
I grinned at the person telling the joke.
Blonde jokes are short because if you were to have a joke that goes on and on the person whom you are telling the joke to will lose interesteds in what you are telling him/her.
It's called a 'knock knock' joke.
Joke Teller: Knock-knock! Joke Receiver: Who's there? Joke Teller: Interrupting cow. Joke Receiver: Interrupting c-- Joke Teller: Moo!!!! :]
Knock knock...
knock knock Who's there? Yes, it was indeed Shakespear that invented the knock knock joke, first using the format in one of his plays. Possibly, anyway.
Whos there
Person 1 - Knock knock. Person 2 - Who's there? Person 1 - Banana. Person 2 - Banana who? (repeat it as shown below) Person 1 - Knock knock. Person 2 - Who's there? Person 1 - Banana. Person 2 - Banana who? (and repeat again) Person 1 - Knock knock. Person 2 - Who's there? Person 1 - Banana. Person 2 - Banana who? (not this time, read carefully) Person 1 - Knock knock. Person 2 - Who's there? Person 1 - Orange. Person 2 - Orange you glad I didn't say banana? This is a good knock knock joke to play on someone if you didn't know it or have never played it on somebody, I guess.
Superguy.
knock knockwho's thereI'm lionthan tell me who you really are then.
knock knock whos there Dork Dork who Dorky Whale