From the beginning, Deux Deux's hat is a red stripe on top of a blue body. When the Inspector shows Deux Deux the room with the mountain of eggs, Deux Deux's hat is a blue stripe on top of a red body. But when the Inspector grabs Deux Deux, the hat suddenly switches back to a red stripe over a blue body.
When the Inspector begins his investigation at Madame's chateau, visually he knocks on the door three times with his magnifying glass, but there is the sound of four knocks.