Deadpan Absurdism
Showing extreme, violent or surreal events while the characters react as if nothing unusual is happening. That mismatch is funny and unsettling at the same time.
The Trouble with Harry
A corpse is an inconvenience for the neighbors, and nobody screams. No one is much upset about Harry's death. That calm tone makes the scenes funny and also a bit eerie.
Fargo
People discuss murder, kidnapping and getting rid of bodies in the same flat tone as restaurant orders and weather reports. Deadpan means saying outrageous things with a straight face, and the Coens' version has nothing cruel in it. It is how the film shows that evil is ordinary, dull and deeply stupid. Marge is competent and normal, and that threatens this kind of evil more than any dramatic showdown would.

