A Night at the Opera (film) DVD commentary. But this could not have occurred, because Sam Marx had died in 1933, during pre-production of "Duck Soup", two years before "A Night at the Opera" was released. The rumor arose because Frenchy had had such a cameo appearance in the Marx Brothers' earlier "Monkey Business". There is, however, a reference to the Marx Brothers' mother, Minnie Marx, during the stateroom scene, in which a woman asks, "Is my Aunt Minnie in here?" Part of the concept of casting the Marx Brothers as stowaways on a ship was recycled from "Monkey Business". As Groucho's and Margaret Dumont's characters
Marx Brothers and the Marx Brothers. Most of the comedians provided their own voices for their animated counterparts, except for Fields and Chico Marx (both had died), and Zeppo Marx (who had left show business in 1933). Voice actor Paul Frees filled in for all three (no voice was needed for Harpo). The Marx Brothers' segment was a reworking of a scene from their Broadway play "I'll Say She Is", a parody of Napoleon that Groucho considered among the brothers' funniest routines. The sketch featured animated representations, if not the voices, of all four brothers. Romeo Muller is credited as having written