When three sons-in-law chase the soon-to-be fourth, Charles, as he goes to the hotel with his sister, they take photos of them entering the hotel and elevator, but when they show Isabelle the photos, they're of them entering the hotel.
Marie tries to please her sons-in-law at the Christmas dinner with one turkey for each (one kosher, one halal, and one Chinese). No private kitchen oven equipment could possibly manage to cook three full turkeys at once.
When Claude and Marie Verneuil are going shopping by car to prepare for Christmas, people in short sleeves are behind their car.