Deadpan (or "Dry Humor") involves delivering jokes with a neutral expression and a monotone voice. No smiling. No energy. No "selling" the joke.
The Contrast
Deadpan works on contrast. * Content: Absurd, crazy, or highly emotional. * Delivery: Flat, emotionless.
Example (Steven Wright): "I spilled spot remover on my dog. Now he's gone." If he delivered this with a wacky clown voice, it would be cheesy. By delivering it like he's reading a grocery list, the absurdity pops.
The Power Control
A smiling comedian is asking for your approval ("Please laugh!"). A deadpan comedian doesn't seem to care. This high-status indifference attracts the audience. We want to make them crack. But they never do.