Duck Soup filmed at Pasadena mansion where Buster Keaton also filmed
Duck Soup has scenes filmed at the lavish Jewett estate located at 1145 Arden Road in Pasadena, the same place where Buster Keaton filmed the opening scene from Cops (1922), and where the noir classic (1947) was filmed. It's also where the Dynasty TV show was filmed. You can read about it at this post.
https://silentlocations.wordpress.com/2015/07/05/groucho-buster-and-noir-at-the-pasadena-jewett-estate/