Entering vaudeville in the early 1920s, Donald Cook matriculated to Broadway in 1926 and came to films in the first years of the talkies. He was a leading man in most of his earliest movie appearances; he played the protégé of crippled ballet impresario John Barrymore in The Mad Genius (1931), Bette Davis' love interest in The Man Who Played God (1932), and so on. By the mid-1930s, Cook had settled into secondary roles, often neurotic in nature (the best of these was the tormented husband of mulatto Helen Morgan in Show Boat ). He often appeared in murder mysteries, where no matter how helpful and cooperative he was to the investigating detectives, the words "I DID IT" were practically emblazoned on his forehead. Throughout the 1940s, Cook alternated his increasingly standardized film roles with solid leading assignments in such Broadway plays as Claudia and Private Lives; he forsook films entirely in favor of stage work in 1950. In 1959, Donald Cook was a regular on the teen-oriented TV sitcom Too Young to Go Steady.