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Clark Gable and Spencer Tracy would go on to make two other films together, Test Pilot (1938) and Boom Town (1940). By the end of the filming of the latter, Tracy had tired of always receiving supporting billing below Gable and insisted on shared billing going forward. Gable did not agree with this, and they never worked together again.
Clark Gable did not want to make this film but he was at the mercy of MGM studio head Louis B. Mayer, who had just paid off one of his numerous paramours.
Clark Gable and Jeanette MacDonald did not get along at all during filming, and avoided each other completely off the set.
Jeanette MacDonald personally chose Spencer Tracy for the second male lead. Previously he had mainly been cast as heavies; this role completely turned his career around.
The song "San Francisco", which was written for this film, is now a popular anthem in the city and is sung on earthquake memorial days.
Jeanette MacDonald brought Anita Loos' screenplay to the attention of MGM head Irving Thalberg, with the express idea that she should headline alongside Clark Gable. Thalberg readily agreed, although Gable did not get along with MacDonald during filming. He objected to her singing at him, and would eat garlic before their kissing scenes just to annoy her.