Deliberate mistake: In the opening title sequence, just after the title of the movie is shown, Puss cuts a P with his sabre into a curtain or flag. In the middle of the P, there is cloth remaining, but since he cuts edges all around this to make the Capital P, this cloth should fall away as it is no longer attached to anything, yet it floats in mid air.
Deliberate mistake: When George Clooney is in the restaurant, he sits down at a booth alone. From a wide shot, he sits down and then they show a close up and he sits down again.