Continuity mistake: During the car chase scene under the "B" Elevated Train in Brooklyn (86th St.), Popeye passes the same curve at least 3 or 4 times. Look closely, you'll probably see the same movie theatre over and over again. Apparently, they rerun the same chase clip to increase the length of this scene.
Continuity mistake: During the car crash scene, the Commanding Officer, Popeye, Detective Russo and the other cop are walking toward the accident. Close shot of Popeye, as he says, "I say we keep sitting on Boca", and they all stop walking. Immediate cut to long shot, and they are all still walking toward the accident.
Continuity mistake: At the start of the movie in France, we see an undercover French policeman shot by Pierre Nicoli, if you look quickly when the policeman is shot, we can see blood splatter all over his face. However, when we see the wider shot of him falling down his face is clean and has no blood on it at all.