Laughter is not an emotion. Joy is an emotion. Laughter is a criticism we hurl at something we find ridiculous or outrageous. It may occur inside any emotion, from terror to love. Nor do we laugh without relief. A joke has two parts: setup and punch. The setup raises the tension in the audience, if only for a moment, through danger, sex, the scatological–a host of taboos–then the punch explodes laughter.
– Robert McKee, Story