Mikael Uhlin's Marxology @ marx-brothers.org

Firecrackers - Character breakdown

Compared with the finished film, most of these character names were later changed. Only the names of Chicolini (Chico) and Mrs Teasdale (Margaret Dumont) were kept. Groucho eventually became Rufus T. Firefly while Harpo played Pinky - although the pressbook named his character Brownie.
Ambassador Frankenstein of Amnesia was soon changed to Ambassador Trentino of Sylvania. The radio trailers (The Paramount Movie Parade) reveal that Zeppo's character remained Groucho's son until very late in production when he became Bob Roland, and that Mrs Teasdale's niece June Parker transformed into Vera Marcal, first introduced as Trentino's "niece", finally becoming his a companion.