Groucho promptly composed a reply. "I had no idea that the city of Casablanca belonged exclusively to Warner Bros," he declared, noting that the average movie fan could probably learn to distinguish between Ingrid Bergman and Harpo Marx. "I don't know whether I could," he added, "but I certainly would like to try." He continued: "You claim you own Casablanca and that no one else can use that name without your permission. You probably have the right to use the name Warner, but what about Brothers? Professionally, we were brothers long before you were... Now, Jack, how about you? Do you maintain that yours is an original name? Well, it's not. It was used long before you were born. Offhand, I can think of two Jacks -- there was Jack of 'Jack and the Beanstalk' and Jack the Ripper, who cut quite a figure in his day... As for you, Harry, you probably sign your checks, sure in the belief that you are the only Harry of all time and that all other Harrys are impostors. I can think of two Harrys that preceded you. There was Lighthorse Harry of Revolutionary fame and a Harry Applebaum who lived on the corner of 93rd and Lexington Avenue..."
Both parties eventually dropped the subject (though not before several other letters were exchanged -- see below). However, when the studio announced the production of the Cole Porter biopic Night and Day, Groucho fired off a final mocking letter to complain; The title, he claimed, was stolen from two Marx Brothers films: A Night at the Opera (1935) and A Day at the Races (1937)!
[Warners replied to Groucho's first letter demanding an outline of the plot of A Night in Casablanca. "There isn't much I can tell you about the story," he wrote. "In it, I play a Doctor of Divinity who ministers to the natives and, as a sideline, hawks can openers and pea jackets to the savages along the Gold Coast of Africa... When I first meet Chico, he is working in a saloon selling sponges to barflies who are unable to carry their liquor. Harpo is an Arabian caddie who lives in a small Grecian urn on the outskirts of the city... As the picture opens, Porridge, a mealy-mouthed native girl, is sharpening some arrows for the hunt. Paul Hangover, our hero, is constantly lighting two cigarettes simultaneously. He apparently is unaware of the cigarette shortage."
The studio soon wrote back complaining that they did not understand the story line. Groucho replied again, explaining that they had made some changes to the plot. "In the new version, I play Bordello, the sweetheart of Humphrey Bogart," he claimed. "Harpo and Chico are itinerant rug peddlers who are weary of laying rugs and enter a monastery just for a lark. This is a good joke on them, as there hasn't been a lark in the place for fifteen years... Across from this monastery, hard by a jetty, is a waterfront hotel, chock-full of apple-cheeked damsels, most of whom have been banned by the Hays Office for soliciting... Harpo marries a hotel detective; Chico operates an ostrich farm. Humphrey Bogart's girl, Bordello, spends her last years in a Bacall house..." It was at this point that the studio finally gave up.]