Comedy is a deadly serious business. We all understand that the best comedies are those that are played absolutely straight, and the worst are those that send signals to the audience that something is intended to be funny. Goofing off, self-pranking, going too broad, etc. It follows that actors must never laugh at anything the audience may or may not laugh at. Signalling that something is funny is called “breaking character” — a violation of the code.

It’s significant, therefore, that in this scene from Stanley Kubrick‘s Dr. Strangelove, perhaps the greatest straightfaced comedy ever made, a serious actor can be seen dropping the ball.

Peter Bull, as Russian Ambassador Alexi de Sadesky, is the violator. It happens at 1:26 or thereabouts. Peter Sellers‘ titular character repeatedly beats his rebellious Nazi arm and Bull, standing nearby with a group of U.S. military officers, can’t help himself — he starts to grin very slightly but then reverts back to sternface. It’s surprising that Kubrick didn’t call for a retake.