I've made up a lot of jokes. I make them up all the time. Some friends have characterized this tendency, with varying degrees of tact, as a neurological disorder.
That notwithstanding, my flagship go-to is my knock knock joke. It actually started as a snide comment to a friend about a guy another friend of ours was dating. But it was funny and I told it incessantly over the next few years, until another friend suggested I submit it to Garrison Keillor's long-running NPR program A Prairie Home Companion for their annual "Pretty Good Jokes" show in 2004.
So I did, and forgot about it till a few months later when a friend called to say she heard it. Since she was on the East Coast I got to tune in three hours later and indeed, he used it to open the show. Amazing, huh??
Oh right, the joke. It works better spoken than written, so I'll let Garrison tell it:
You caught the part where he called it "a whole new class of knock knock joke," right? Yeah, I thought that was cool too.
If that file didn't work, or you're in a coffee shop and don't want dirty looks, here:
Control freak. Now you say "control freak who?"
One quirk of this joke: about a quarter of the time people will just stare at you blankly and say "control freak who?" That gets awkward. But after my joke aired I Googled it and was delighted to see that some stranger had solved that problem: If someone says "control freak who?" you just say "No, no, like this: control freak who?" over and over, and get more impatient and interruptive till the person finally either gets it or stalks off. Sometimes that's more fun than when they do get it.
It is a weird and heady thing to have fathered a joke, and to know where one came from. PRC used it in a sketch a year or two later, and it turned up in the Pretty Good Jokes Book. Of course I can't absolutely prove it's mine...that's the nature of jokes. I once had a woman tell it to me and when I said I made it up she didn't believe me. Which, frankly, was kind of cool. I wouldn't have believed me either.
Garrison never did sent me the five bucks you're supposed to get when they use your joke. But after pestering his assistant for a year I got the picture at right, which frankly I would have paid more than five bucks for, so it's all good.