The "hanging from the clock tower" stunt is a homage to Safety Last! (1923). At least three different takes were shot; two are shown during the course of the film, and a third at the end under the credits.
In rehearsal for the clock tower fall inspired by Safety Last!, Chan took a week to build the courage to drop from such a great height. During the shooting of the bicycle chase sequence, one of the stuntmen informed Chan that E.T. the Extra-Terrestrial was playing at the local cinema. Chan halted filming to watch the bicycle chase scene in the finale of E.T., to ensure that his scene and Steven Spielberg's scene were not the same. After watching the film, Chan became more confident, realizing that the audience doesn't really care so much about such minor details, only in watching the film and having a good time. According to his book I Am Jackie Chan: My Life in Action, Chan injured his neck while filming the scene.
Regarded as one of the most ground breaking movies in Hong Kong Action cinema. Up to this point, Hong Kong movies didn't have the big scale sets and attention to period detail that was lavished on this film. And it was the first to have a mixed variety of action sequences and not just rely on martial arts, which pretty much set the tone for the rest of Jackie Chan's movie career.
The scene where Jackie Chan emerges from the barrel of water was part of a much longer sequence that didn't make the final cut, where he and Sammo Hung are chased to a brothel by the army. Then after Chan is shown fully dressed, a fight took place in and around the brothel after he and Hung were handcuffed together. Most of the ideas were re-used by Chan for Project A Part 2, in the sequence where he and a fellow officer are handcuffed to each other and are trying to fend off a gang.
The U.S version distributed on video and DVD by Miramax's studio division "Dimension Films" in North America in 2000, it has a new opening credits sequence, a new score, and dubbed English dialogue. In addition, seven minutes are cut from the original dialogue (105 Mins) to 97 Mins.