The peppers that Jackie Chan chews on and later rubs in the eyes of the attackers were real. The prop department were supposed to make up fake peppers, but weren't able to complete them in time for the shoot.
Sammo Kam-Bo Hung and Biao Yuen do not appear in this movie because they were filming Operation Eastern Condors (1987) at the same time this film was in production.
The scene in Yesan's (Maggie Cheung's) house is an homage to the Marx Brothers' A Night at the Opera (1935), where everyone was crammed into a ship cabin.
The "scene from bring the down house" stunt is a homage to Wasser hat Balken (1928) and several takes were shot.
Isabella Wong is the only rare model character to appear in Project A (1983) and this movie, and has not been seen in any other movies. Wong had a cameo appearance in Police Story 2 (1988).
Roberta Chow: Second Assistant Director and Producer Raymond Man-Wai Chow's daughter appeared as Woman Walking in the Park with Her Man.