Oh, and knock-knock jokes were huge:
Knock knock.
Who’s there?
Lettuce.
Lettuce who?
Lettuce in, it’s cold outside!
There’s also the standard:
Knock knock.
Who’s there?
Orange…
ETA: (not when I was in high school. These here are genuine kindergarten jokes.)
Earliest joke I can remember: What’s the scariest job in Translyvania? Dracula’s dentist!
I remember it because it was the first joke on the first page of a book I bought at my first grade book fair, 101 Monster Jokes.
Another old one I’ve actually liked goes like this: A horse walks into a bar. The bartender asks, “Why the long face?”
Oh, and here’s another one that I like: What’s brown and sticky?
A stick!
Some fun posts, people! Allow me to ask an additional question, please.
At what age did the Little Moron joke lose its primacy to the Little Johnny joke? I suspect that transition marks the Age of Awareness for many.
My favorite Little Johnny and one of the first I heard ended with “Rats, Teacher! (and proceeded with a few well-chosen expletives)”
To me, Dirty Ernie = Little Johnny.
The first joke I remember:
So, a teacher tells her students to go home and learn the first four letters of the alphabet. So the kid goes home and asks his mom, who’s on the phone, “What’s the first letter of the alphabet?” and the mom replies, “Shutup!”
He asks his sister, listening to music with her headphones, “Yeah, yeah yeah!”
Brother, playing video games, “nu nu nuh nun nu nun BATMAN!”
Dad, taking out the trash, “In the garbage, in the garbage!”
So the next day the kid goes to school, and the teacher asks him what the first letter of the alphabet is. “Shutup”
“Young man, do you want to go to the principal’s office?”
“Yeah, yeah yeah.”
So he gets to the principals, and the principal says “Young man, who do you think you are?”
“Nu nu nuh nun nu nun BATMAN!”
“I’m going to have to go to your house and talk to your parents! Where do you live?”
“In the garbage, in the garbage!”
The earliest joke I can remember is, “Why is marble always sad? Because people take it for granite.”
::rimshot::
Yeah, what the hell. I was seven.
Grabs someone’s head an massages it
“What’s this?”
Victim" `Er, I don’t know."
“A Martian brainsucker, starving to death”
My first joke: “Doctor, I’m not well”
“Well this medicine will cure you but you must take it religiously”
Patient comes back a week later sicker than ever.
Doctor: “Did you take your medicine? I told you to take it religiously”
Patient: “But doctor, I’m am atheist!”
Not bad for an 8 year old I think 
Try this out on kids under 8 or so…
Tell them the chicken crossing the road joke. Then say, “Now, you tell me a joke”.
They will almost always structure their joke like it. They’ll say something like, “Why did the dog cross the road? To get a bone”.
It’s interesting to see how their minds work. And, of course, always tell them you like their joke.
The first jokes I can remember were Little Moron jokes, e.g.:
Why did the little moron throw the clock out the window?
He wanted to see time fly.
Stuff like that.
There were a couple I thought was pretty funny even though I didn’t really get them:
What did the mayonnaise say to the ketchup?
Close the door, I’m dressing!
(I never thought of mayonnaise as any kind of “dressing.”)
And:
When is a door not a door?
When it’s ajar.
It took a few years before the penny dropped for me on that one.
Those all ring bells with me, too.
I guess kids are in the process of adapting to a language that has a lot of ambiguities and multiple meanings and spelling conventions and all that. It makes me wonder if kids whose native tongue is less confusing go through similar stages of getting into humor. For that matter, is humor (jokes, anyway) substantially different in other languages. I seem to recall some joke (Monty Python may be the source) that was hilarious in German but a dud in English.
I must tell you: that’s the joke. Sorry to have wrecked the rest of your life. 
Hahahahahah! =Gasp!=
That’s so funny I think I’m laughing myself to de
::thud::
Knock knock.
Who’s there?
Marcella.
Marcella who?
Ma cella’s full of water; better call the plumber.
After watching star wars I remember coming up with this side splitter:
what do you get when you cross a monkey and a cookie? a Wookiee!
My elder brother was (is!) football mad (UK Football. Not Pansy Rugby) and collected cards that had the vitial statistics of each player on them.
While I was working on the football manager program on our Amstrad CPC464 (using these stat cards) our mum comes out and asks what we’re doing. I explain. She holds a card up and asks “who’s he”. I reply “He’s a virgin” . A little surpised by my responce, given that I was 11 years old, my mum asks “How do you know?”
And I reply : “Cliff Richard told me”. My mum thinks this is very very funny, but I’ve no idea why. I don’t even know why I said he was a virgin, let alone why I thought of Cliff Richard. I must have heard something recently about that old dude.
Looking back the whole thing is weird, but I was so proud at the time that I’d told a joke that made an adult laugh! My brother was most un-impressed.