Nanette (1940)

Alexander Patou is a very successful playwright; he has decided he needs to get fresh material for his next work, and to do so he will go incognito among ordinary people. He chances to meet the fiery Nanette Dürwaldt and her hulking boyfriend Gustav. Attracted to her, Patou quickly ends up injured by Gustav, and he persuades Nanaette to let him stay in her spare room. As the first night turns into a week, he secretly starts writing the next play, involving her as the leading character. She discovers him writing the manuscript, and when he is evasive about it, there is a quarrel. There's worse ... Patou was singing a love serenade down the phone last night to his theatrical agent, as an idea for the play; Gustav has heard this and has told Nanette that Patou is wooing another girl.