There are various accounts of why Marlene Dietrich was cast as Lola Lola, but the one given by director Josef von Sternberg in his autobiography is that Dietrich came to test for the film with a bored, world-weary attitude because she was convinced she wasn't going to get the role and was merely going through the motions - and Sternberg hired her because that world-weary attitude was precisely what he wanted for the character.
Josef von Sternberg and Marlene Dietrich's love affair, which began during production of this film, caused quite a tabloid scandal and ultimately led to the dissolution of von Sternberg's marriage. On March 31, 1930, the night of the film's triumphant premiere in Berlin, the couple absconded to New York in order to begin a film career together in the United States. Von Sternberg's wife, Riza Royce, discovered the plans and arrived in the United States before her husband and Dietrich. She and her lawyer met the couple at the dock as they disembarked from their cruise liner. Royce served Dietrich with papers notifying her that she was being sued for libel and alienation of affection, and she filed for divorce from von Sternberg one month later.
Emil Jannings grew resentful of the special attention director Josef von Sternberg showed to Marlene Dietrich. He would purportedly throw tantrums on set and once threatened to choke the leading lady.
Marlene Dietrich's screen test for this film survives. In it, she pretends to upbraid her pianist, played by Friedrich Hollaender, the film's composer. She then sings the chorus of "You're the Cream In My Coffee" a number of times, in English, after which she climbs on the piano, hitches up her skirt (to show her legs) and sings, in German, a torch song called "Why Cry" by Peter Kreuder, a well-known song-writer who supervised the film's orchestral arrangements. As the test ends, Dietrich breaks character and apologizes to Hollaender.
Emil Jannings' first film back in his native country after an abortive trip to Hollywood. Hoping to become a star of American films, Jannings was soundly rebuffed because no one could understand his accent.