When Jackie was doing the stunt at the clock tower, he was afraid of falling voluntarily. So he held on until he literally lost his grip and fell.

Jackie Chan had no intention of making a sequel to this movie, but the Japanese Emperor enjoyed the movie so much, he told Chan he was looking forward to it, so Chan felt obligated.

In rehearsal for the clock tower fall inspired by Safety Last! (1923), 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 (1982) was playing at the local theater. 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 groundbreaking 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 movie. 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 "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.

Dick Wei was seriously injured during filming the climatic fight when Sammo Kam-Bo Hung kicks him in his back.

One of the stunts, involving a fall from a tower, almost cost Jackie Chan his life.

Jackie Chan did the stunt scene at the clock tower three times.

The first movie in which Jackie Chan started using outtakes in the end credits, which is an idea he liked after working on The Cannonball Run (1981) in Hollywood.

Originally going to be titled "Pirate Patrol", but it was feared that once announced, other Hong Kong film producers would rush to copy and release movies featuring pirates.

Grossed fourteen million dollars in two weeks, which was a new record at the time for a Hong Kong movie.

Marks the first time that Siu-Tin Lai used orchestral music instead of library music or music lifted from other movies.

The first Hong Kong movie where Jackie Chan opted for a more naturalistic, street fighting style rather than the traditional Kung Fu in his earlier movies.

Sammo Kam-Bo Hung's introduction scene, where he's playing Mahjong, was cut from the international releases, because it was felt foreign audiences wouldn't understand the game.

Was Danny Trejo's film debut. (voice only)

The movie's title, "Project A", was originally a working title.

Jackie Chan and composer Siu-Tin Lai's first collaboration.

Prior to filming, Jackie Chan and his stunt team trained with the real marine police to give a sense of authenticity to the squad's marches.

The U.S version distributed on videocassette 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, eight minutes are cut from the original dialogue (one hour and forty-five minutes) to one hour and thirty-seven minutes.

This movie was adapted as a television series in Hong Kong with the same name.

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 Kam-Bo 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 2 (1987), in the sequence where he and a fellow officer are handcuffed to each other and are trying to fend off a gang.

Edward Tang and the production team felt that a period movie could still have success if it had sufficient action, and so researched the history of Hong Kong during the time of pirates for this movie.