Comedy is hard.
Any actor who has stood in front of an audience and watched a line that he practiced for weeks, clang helplessly to the floor to roars of silence, will appreciate Sir Donald's sentiments. Comedy is hard because we don't really understand what makes people laugh. We know what's funny because we laugh at it. But trying to distill the essence of comedy into a set of principles or laws is not so easy. One of the basic elements of comedy is incongruity.