Revealing mistake: Foussard is killed and his body dropped off the cliff into the sea. There is a close-up shot of his head and torso, facing upward, that is supposed to be underwater. However, the actor is obviously not in water. His hair, that should be floating loosely around his head never moves and appears to be held in an outward position by stiff hair gel. Some type of "special effect" filter is layered over the entire shot to simulate water rippling over the corpse.
Revealing mistake: When Cary walks into the office of the restaurant of his friend, the egg is thrown from Cary's left yet the camera/Cary only looks at the people to his right in the kitchen.
Revealing mistake: When Cary Grant walks into the office of the restaurant of his friend the kitchen has the center island to the right of the dishes tray, right of the light, and right of Cary's view to the dishwasher. There is a single row of dark tiles between the island and the cooks in blue. Later when the dishwasher turns and walks toward Cary the center island has been moved to the left. It is left of the dish tray, left of the light and is now showing three rows of dark tiles between the island and the cooks in blue.