Answer: Ralph Bellamy and Don Ameche
In the movie "Trading Places", Ralph Bellamy and Don Ameche played the roles of the Duke Brothers, Randolph Duke and Mortimer Duke respectively.
Ralph Bellamy was a famous actor during the Golden Age of Hollywood who began his acting career as a theater actor. He began his film career in 1931 with the film "The Secret Six". Some of his well known films are: "Rebecca of Sunnybrook Farm" (1932), "The Awful Truth" (1937), and "His Girl Friday" (1940). He also acted in a number of television shows such as "Man Against Crime", from 1949-1956, "The Eleventh Hour", from 1963-1964, "Wheels" and "The Winds Of War".
Don Ameche was also a well known actor, who acted in theater, films and television. He made his debut in films in 1935 with the film "Clive of India". Some of his other well known films are: "Ramona" (1936), "Ladies in Love" (1936), "Love Is News" (1937) "Slightly French" (1949) and many other films. He acted in TV shows such as "The Polly Bergen Show" and "The Greatest Show on Earth"