Groucho Marx told an anecdote - both on a '60s Today Show segment and in print - that the movie's producer asked three aspiring actresses to walk seductively past Marx. Whomever Marx decided was the best walker would play opposite him in the film. When the third girl walked past, Marx asked the producer, "How could you possibly choose anyone but that last one?" Marx had chosen Marilyn Monroe for the film.
Groucho hated the finished film so much that, in his autobiography "Groucho and Me," he refers to Una notte a Casablanca (1946) as his final film with his brothers.
This is the only Marx brothers movie in which Groucho Marx has a real mustache; in the other films, Groucho used greasepaint for the mustache effect.
"Love Happy" is the last official Marx Brothers film.
Despite being a "Marx Brothers" movie, at no point in the film do all three Marx Bros. - Groucho, Harpo and Chico - appear in any scene together. The closest instance of this happening is near the end of the film when Harpo and Chico walk past Groucho's hiding place on the rooftop. However, Groucho is not seen until after his brothers have walked by. Harpo shares scenes with Chico and a few with Groucho, while Chico and Groucho share only one (the final scene in the film).