"YOU don't have to be mad to work here, but it helps!"
Take one softly spoken, power crazed, psychotic nurse and a pair of moronic, sadistic aides and let them lord it over a bag of assorted nuts and everything works out just fine.
That is, until they let the aggressively male, exuberant (but relatively sane) R.P. McMurphy, into the mad house, then all hell breaks loose.