The police station was filmed on the fifth floor of West Island School in Hong Kong. The meeting room is the study room of the upper school area, and it also doubles as the infirmary. Other scenes take place right outside of that room. In fact, you can see the blue lockers in the background.

After the fight in Daniel's (Daniel Wu's) bar, Match (Stephen Fung) asks Alien (Sam Lee) why he disabled a gun he'd taken from one of Daniel's thugs instead of using it, to which Alien responds that that's what Jackie Chan always does. Jackie Chan is one of this movie's producers and has a small appearance at the end.

Because of their command of perfect English, Nicholas Tse, Stephen Fung, Daniel Wu, and Terence Yin dubbed their own voices for the English dubbed audio track of the movie.