The movie studios currently promote their coming attractions through press junkets. The star sits in some hotel room with a poster or prop from the movie in the background, and then a zillion reporters are run through the room for a quick “exclusive interview”. Paul Newman likened the experience to being double parked in front of a whorehouse.
But before air travel was cheap enough to allow reporters to participate in the current junket system, the studios relied on trickery. Movie stars would be shot talking on the telephone on the right side of a split screen, and would answer questions written by the studio. The scripted questions would then be shared with members of the press, who would be filmed doing the left hand side of the screen, as if they were getting an exclusive telephone interview with the star.
That is the source of this clip of Peter Sellers during the making of my all-time favorite movie, Dr. Strangelove. The scripted question he is answering was to do some British accents for American audiences and he puts on an absolutely stunning display of verbal skill in response.