Andy Hui's character, Kei-on is a combination of two characters from Japanese Comic, Doreamon, which are Suneo (where Andy Hui gets the weird hairstyle and wealthy background) and Giant (in the Cantonese version of Doreamon, Giant is called Kei-on and he is a big bully). Dicky Cheung's character is also a reference to Doraemon's main character Nobita (Cantonese version is called Dai-hung, always a bully victim of Giant and Suneo), and Charlie Yeung's character is obviously refers to Shizuka (Nobita's love interest in Doraemon). In fact, in the film there is also a reference to Doraemon comic. Once Hung discover the identity and ability of those three 'future cops' he exclaim that "it is just like Dai-hung (Nobita) has three Ding-dong (Doraemon's name in Cantonese) altogether!"