Comedy relies on expectation. You expect a punchline. Anti-Humor relies on violating that specific expectation by delivering... absolutely nothing.
The Shaggy Dog Story
The classic form of anti-humor is the "Shaggy Dog Story." It's a long, rambling, detailed narrative that builds up tension and anticipation, only to end with a pointless or anticlimactic conclusion.
Example: A boy asks his dad for a plum. The dad says no. The boy asks again. The dad says, "If you ask again, I will nail your ear to the wall." The boy asks again. The dad nails his ear to the wall. The boy says, "Dad? Can I have a plum?" The dad says, "You can't reach it."
Is it funny? debatable. The humor comes from the audience's frustration. You wasted their time, and the sheer audacity of that waste becomes the joke.
Why Chicken? Why Road?
"Why did the chicken cross the road? To get to the other side."
This is the ultimate anti-joke. It sets up a riddle, and the answer is a mundane statement of fact. It parodies the structure of a riddle itself.
Modern Anti-Humor: Norm Macdonald
The late Norm Macdonald was the king of this style. He would go on talk shows and tell 5-minute stories with no punchlines, delivered with a cheesy grin. He forced the audience to laugh at the awkwardness of the silence rather than the content of the words.
Anti-humor is comedy for comedians. It deconstructs the art form.