La Doublure (2006)

Caught by tabloid paparazzi with his mistress Elena, a famous and beautiful fashion model, billionaire Pierre Levasseur tries to avoid a divorce by inventing a preposterous lie. He uses the presence of a passerby in the photo to claim to his wife that it's not him Elena is seeing but the other man, one François Pignon. Pignon is a modest little man who works as a parking valet. To make the story convincing, Elena has to move in with Pignon.