Learning to be Funny...Knock Knock Jokes!?

We are very into "knock knock" jokes in our house. Like this:

Knock knock.
Who's there?
Who.
Who who?
Is there an owl at the door?

Knock knock.
Who's there?
Boo.
Boo who?
Why are you crying?

Okay, they're not great humor. But my almost 6-year-old is in love with them. He really doesn't always understand any that are more complicated than the ones above...but I'm having way too much fun with them. Who knew that there were so many knock-knock jokes online!? And, wikipedia even has an entry for the knock-knock joke. Wowza.

When my brother was little, he was not very good at telling jokes. In fact, we made him preface all jokes with "this is a joke" so that we'd know we should laugh and not make him feel bad. It took a while, but now (he's 22), he's finally got it:-) It just goes to show that you can learn to be funny.

So how do you teach your kids to be funny? How do you teach them to tell a joke? I think it's a pretty important skill...what do you think?

P.S. Someone in my office told me that about once a month as her kids were growing up, they would have a monthly "joke night" during which each kid would stand up and give his or her "routine" for the family...training stand-up comedians?
P.P.S. My dad, the funniest guy I know, is celebrating his birthday today...Happy birthday, Dad! Thanks for teaching me to tell a good joke!