Jones starred in many film musicals during the 1930s and 1940s. The best-known of these were the original film version of "Show Boat" (1936), and "The Firefly" (1937) in which he sang what would become his signature song: "The Donkey Serenade". He is probably best remembered today as the romantic lead opposite Kitty Carlisle and Maureen O'Sullivan respectively, in the first two films the Marx Brothers starred in for Metro-Goldwyn-Mayer: "A Night at the Opera" (1935) and "A Day at the Races" (1937), filling a straight-man role opened by the departure of Zeppo Marx from the team.