Another type of humor that works well in fiction is having a character forced to pretend to be the exact opposite of what he is.
The prissy heroine may don dirty jeans and boots and do an earthy cowgirl impression to impress a potential client. This scene pushes the character out of her comfort zone as well as allowing her to see her own ridiculousness in both roles.
If you can play against type as well as situation, you can give the reader a double treat.
In this scene from an unpublished novel, two alpha males are escaping from a hospital although one of them is so badly hurt he should be admitted, not trying to leave, and he had come into the hospital to kill someone so the situation is twisted, as well, into irony, another humor element.
Cole and Daniel staggered into the sanctuary of the empty elevator, and Cole hit the lobby button with his elbow.
When the door closed, he let Daniel slump against his chest, and he held him up with both arms. Daniel's legs buckled completely, but Cole was afraid to tighten his hold for fear of the fractured ribs.
The elevator clicked, and a light came on above the door.
"Oh, lord. We have company," Cole said.
Daniel tried to straighten his legs, but they bowed like a drunken cowboy's.
"Stay where you are." Cole pulled him back up. "And for pete's sake, hide that famous face of yours, darling."
Tittering drunkenly, Daniel buried his face in Cole's blond hair, then nuzzled his ear, his arms snaking around Cole's waist and neck.
"Don't be fresh," Cole muttered as the door opened at three. A well-dressed, middle-aged couple walked in.
"Hello," Cole gushed cloyingly and grinned, careful to keep his own famous face in shadow.
When she saw the two men in intimate embrace, the graying matron backed into the already closed door.
Cole purred proudly, "We're being married tomorrow."
The gentleman shoved the next floor's button instead of the main floor.
Cole fought to keep a straight face and Daniel on his feet.
The elevator door opened, and the couple rushed out.
"Damn, they've left," Cole complained. "I wanted to invite them to the wedding."
"What will Penn and Lylah say? They don't even know we're dating."
Cole's laughter got them through the lobby and outside the hospital.