The first rule of acting in a comedy is that you don’t laugh at what anyone else says or does. Ever. Straight and sober from start to finish. But look closely at the face of Peter Bull (the “Russian Ambassador” in the black hat, standing to Peter Sellers‘ rear right) at the 17-second mark, and you’ll see him lose it and start chuckling…and then he sobers up again. This is almost the kind of thing that you see in closing-credit gag reels.