My Wife's Name Is Maurice (movie, 2002)

Georges, a wealthy Parisian, has a mistress who wants to marry him, but he has no intention of divorcing his wife, the source of his money. The mistress, meanwhile, has a jealous boyfriend, so when Georges dumps her, two people are angry with him. Add Georges' wife, who suspects the affair. The mistress calls Georges to say she's coming to tell his wife everything, so Georges asks Maurice, a stranger who's passing by, to pose as his wife and scare off the mistress. In this farce, nothing goes as Georges plans.