Love Crazy (1941)

A happily married architect, Steve (William Powell), and his wife, Susan (Myrna Loy), plan a romantic celebration for their fourth anniversary, but their evening is interrupted when Susan's meddling mother, Mrs. Cooper (Florence Bates), stops by for a visit. Later, when Mrs. Cooper eavesdrops on Steve talking with an old flame, Isobel (Gail Patrick), she tells Susan, who files for divorce. Steve, still in love with Susan, decides he must feign insanity to stop the divorce proceedings.