Speaking of chicken and road jokes one of my favorites was told to me by a russian exchange student.
Why did the monkey cross the road?
because it was stapled to the chicken.
and he followed that joke with.
Why did the monkey fall out of the tree?
because it was dead.
Why did the second monkey fall out of the tree?
because it was stapled to the first monkey.
And why did the third monkey fall out of the tree?
Monkey see, monkey do.
I had a similar experience. Me and my buddy were cruising down route 80. He was driving, I was in the passenger seat. He nudges me and points his thumb out the drivers side window saying, “Can you believe this clown is trying to pass us?”
I looked over and saw a clown in full costume trying to pass us in the left hand lane. I laughed for a good ten minutes, not understanding how my friend could have given such a deadpan setup without cracking up himself.
But what if hrhomer’s wife really is an airplane?
The Aristocrats.
The Big Orange Head joke is an all-time fav.
I like the anti-racist-jokes too:
What do you call a black guy flying a plane?
A pilot, you racist.
I think this one works as a typical joke, and an anti-joke:
What’s the difference between an astronaut and Michael Jackson?
One walks on the moon. The other’s a pedophile.
And a couple from the website:
How do you confuse a blonde?
Paint yourself green and throw forks at her.
If life hands you melons, you might be dyslexic.
That site has some good jokes.
Roses are Red. Violets are blue. I am a dog.
Then she’s telling it wrong.
How many feminists does it take to screw in a light bulb?
One, you got a problem with that?
It’s rare that I literally LOL over something I read on the Internet, but just picturing this had me laughing for some time. 
How many flies does it take to screw in a light bulb?
Two. Don’t ask me how they got in the light bulb.
An anti-riddle from A. A. Milne:
Question: “Why does a chicken?”
Answer: “I don’t know.”
I read this whole thread and now I want my…hour BACK…GET IT?!
This one made me LOL for realsies but when I told it to my husband he just stared at me.
I believe it was E.B. White who said “you can dissect a frog or a joke, but both die in the process.”
I worked a job with some roadies who had just come from working the Phillip Glass opera “Einstein on the Beach.” They said the following was Phillip Glass’s favorite joke in the world and he never got tired of telling it:
knock knock
who’s there?
knock knock
who’s there?
knock knock
who’s there?
–keep repeating “knock knock,” prompting the knockee to say “who’s there” until the knockee either laughs because they get it* or gives up in frustration–
*Creating a repetitive exchange IS the joke. This is an anti-joke that’s transformed into a real joke when you know something about the joke teller – here, that Phillip Glass writes very repetitive music.
Same here. If I’d been driving I think I would’ve killed us.
You can pair the ‘what’s brown and sticky’ joke with:
What do you call a boomerang that doesn’t come back to you?
A stick (or “another stick”).
I like to use a really disgusted tone for the punchline.
Funny ones from a previous thread: http://boards.straightdope.com/sdmb/showthread.php?t=616447&highlight=Anti-joke
OP don’t feel bad. I didn’t get the joke either.
Heard on Talk Talk with Jerry Galvin years ago:
How many Californians does it take to screw in a lightbulb?
They don’t- they screw in a hot tub.
I heard the Phillip Glass one as:
Knock knock.
Who’s there?
Phillip Glass.
Phillip Glass, who?
Knock knock… (Ad nauseum.)
This usually gets an explosion of laughter during the second iteration if your audience knows Glass’ work. Although it isn’t really anti-humor, it’s a real joke with a diffused punch line.
–Cliffy