Continuity mistake: Much of this movie was shot in Luxembourg, not in Paris. This is obvious on several occasions - the road signs are clearly not like the French standard. You even see a sign to »Trier (Trèves)«. In Paris, there would be no signs to this German town...and even if there was, these would say »Trèves«. The buses also have French registration plates but are from Luxembourg companies.
Continuity mistake: At the cafe when Serafine says about Andy's friend coming along to "witness you score" Andy drops his coffee cup and you hear it breaking. When the condoms go onto the table the coffee cup is perfectly intact.
Continuity mistake: When the werewolf jumps in front of the subway train, the woman in the purple top drops the same paper bag full of fruit twice. Once viewed from the side; once viewed head on.
Continuity mistake: On the train in the beginning, when Andy is looking at a map, the picture at the top of the map changes between shots. First, there's a little land and a lot of water at the top, then there's all land at the top.
Continuity mistake: After fighting the werewolves in the crypt, Andy goes back to the house and he has a cut on his right shoulder. However, when the werewolves turn up, he runs down the stairs and the cut has now disappeared.
Continuity mistake: Andy's glass jumps from his hand to the table after the toast on the train.
Answer: Claude says in anger while choking him, "Depuis quand tu laisses partir mes invites, Jacques?", which in English translates to, "When did you let my guests go, Jacques?"