Effective light comedian of '30s and '40s films and '50s and '60s TV series, Robert Cummings was renowned for his eternally youthful looks (which he attributed to a strict vitamin and health-food diet). He was educated at Carnegie Tech and the American Academy of Dramatic Arts. Deciding that Broadway producers would be more interested in an upper-crust Englishman than a kid from Joplin, Missouri, Cummings passed himself off as Blade Stanhope Conway, British actor. The ploy was successful. Cummings decided that if it worked on Broadway, it woul…