Deadpan is a funny word. I have always wondered about it.
Here is some information on deadpan.
Wikipedia has a concise definition of deadpan:
a form of comic delivery where humor is presented without a change in emotion or body language. Usually the delivery is in a casual, monotone, solemn and mater-of-fact manner.
The person speaking is calm, detached and displays no personal involvement in what is going on.