An electrician for Warner Bros. studio came up to Paul Muni after an advanced screening of the film and told him that his nine-year-old son asked him to buy him a microscope because of Muni's performance. Even though he went on to win the Oscar for his performance, Muni said that this was the greatest compliment he had ever received and that all other accolades meant nothing compared to that one.
Hal B. Wallis originally rejected Sheridan Gibney's script. He wanted the movie to be a college romance. Star Paul Muni had script control in his contract, so he wrote across the top of the screenplay, "I approve this script as written." Warner Bros. had to film Gibney's original script, which went on to win an Oscar. (From "Film Crazy" by Patrick McGilligan, St. Martin's Press, 1983; and "Actor: The Life & Times of Paul Muni" by Jerome Lawrence, 1974.)
This film propelled William Dieterle to the top rank of directors at Warner Brothers, meaning he was given the plum assignments. Fellow European émigré Michael Curtiz (Dieterle was German, Curtiz was Hungarian) was also in this exclusive club.
After playing a series of hard-bitten roles in films like Scarface (1932) and Black Fury (1935), Paul Muni lobbied hard for a change of pace. Jack L. Warner, head of Warner Brothers, wasn't keen on his star taking such a change of direction but eventually relented, effectively opening up a tidal wave of biopics that became the mainstay of Warner Brothers' output in the late 1930s and early 1940s.