Audiences in 1950 had no trouble identifying where the somewhat ungainly title came from. It's from the fourth line of a well-beloved folk song, not heard much anymore: "Oh, dear, what can the matter be?/ Dear, dear, what can the matter be?/ Oh, dear, what can the matter be?/ Johnny's so long at the fair." It's no stretch to understand who Johnny is in the movie: It's Jean Simmon's character's missing brother, Johnny, and he certainly seems to have overstayed his welcome at this Paris World's Fair.