Idiot's Delight (1939)
Directed by Clarence Brown, and written by Robert Sherwood, this average "musical" comedy features Clark Gable and Norma Shearer, Edward Arnold, Charles Coburn, Joseph Schildkraut, Burgess Meredith, and Virginia Grey (among others).
Gable (as Harry Van) returns from World War I a song and dance man unemployed. He works job to job until he lands with a traveling group running a mind reading gag with Madame Zuleika (Laura Hope Crews). When she's too drunk to perform, Shearer as Irene Fellara, an acrobat in the show, tries to help but exposes Gable's trick, causing him embarrassment. However, she charms him into a dinner date and tries to sell him on using her as Zuleika's replacement. They share some magic but part ways, presumably forever.
Gable continues working job to job and years later is headlining with "Les Blondes", five girls he has trained in a song and dance show touring pre-World War II Europe. While in a town in the Alps under German control, WW II breaks out. The guests at the hotel include Coburn as a scientist, Schildkraut as the German Captain in charge of the region, Meredith as a Chicken Little-ish American (ugh!), and Arnold as an arms supplier with a Countess in tow. The Countess looks remarkably similar to the girl Gable met years ago, and is in fact Shearer as a platinum blonde (doing the worst Greta Garbo impression you've ever seen). Gable tries to solve the mystery of this woman and/or tries to get her to admit who she is, while the war proceeds. A German bomber squadron, which was responsible for helping to start the war, is located in the valley below the hotel. A counterattack is anticipated. The film has two different endings, one for American audiences and one for the rest of the world.
Gable dances and sings "Puttin' on the Ritz" in this film; Grey plays one of the blondes.
*** SPOILERS ***
One ending has Shearer & Gable singing a hymn (not credited) together while bombs are exploding outside the hotel as war planes fly over, etc.; the other has the bombing raid stop, after much destruction, with Shearer & Gable singing a much more upbeat, catchy tune as if (an all consuming soon to be World) war had not just begun.