Jackie Chan was injured during the shooting of this movie. This explains why he is, unusually, doubled quite extensively in some of his fight scenes and for some stunts. Originally, Jackie's fight with Richard Norton was supposed to be the final fight in the movie. Due to Jackie's injury, Sammo Kam-Bo Hung was swapped in to take over fighting duties with Richard. This is also why he's doubled by both Chin Kar-lok and Chow Gam-kong parts of the car-to-foot chase with Norton about an hour into the film.
The injury that prevented Jackie from doing his fight with Richard Norton was damaging his seventh and eighth vertebrae and dislocating his pelvis from sliding down the seven story pole in Police Story (1985).
In Germany, this movie is known as part two of the "Powerman" trilogy with Der Powerman (1984) being part one, and Powerman 3 (1985) being part three. Tokyo Powerman (1985) ("Tokyo Powerman" in Germany) is not part of this imaginary series. Despite the fact that the movies share many of their main and supporting actors, as well as staff members, the characters and storylines are totally unrelated.
Despite many releases of the film proclaiming this to be a film starring Jackie Chan, he doesn't actually appear until over a half hour into the film in a supporting role.
Despite this film being released nearly a year prior, this film uses a music cue originally composed for No Retreat No Surrender. At the end of the finale when Yuen Biao manages to stop Chung Fat's escape via elevator, a fast paced music cue kicks in. This is the same cue as the one at the end of the fight between Jean Claude Van Damme and Kurt McKinney in the original Seasonal Films export cut of No Retreat No Surrender. While that cut of NRNS does borrow some music from Hong Kong films (such as Project A), this specific music cue in question was confirmed to originally be composed by Frank Harris in 1985. It's most likely that, since frequent Sammo Hung collaborator Corey Yuen was in post production on NRNS at the time, Sammo may have seen Yuen's early cut of the film with this first music score and asked to use this cue. By the time NRNS received its American release in 1986, Harris' original music score was replaced for New World Pictures by Paul Gilreath, thus making the Harris cue seem like an original piece for Twinkle Twinkle Lucky Stars.