BODYGUARDS AND ASSASSINS (SUP YUET WAI SING) adds another mystery actor Jacky Cheung Hok Yau, who in the film played the pillar revolutionary, Revive China Society president Yang Quyun. One day after school when Yang Quyun was answering questions from students, a Qing Dynasty assassin assassinated him in the corridor. Hok Yau's death opened BODYGUARDS AND ASSASSINS. Producer Peter Chan Ho Sun said with humor, "When I formed UFO in Hong Kong, the founding film was Cheung Hok Yau and (Tony) Leung Chiu Wai's DAYS OF BEING DUMB (AH FEI YU AH GEI). That film was a huge box office success. So this year when I formed Cinema Popular in the Mainland, of course I thought of them for the film in hopes of they can still bring luck!" Hok Yau said, "At first Peter asked me if I was interested in a guest star role, I said then I would play pedestrian A. He told me, he didn't have pedestrian A, only revolutionary A. When I saw the script, I knew I couldn't escape death. Yet I never thought, Peter would let me die such an awkward death. In the script, Hu Jun shot me as soon as the scene started. I thought that I just lay there after the shot and that was it. Yet I learned only when I got there that the location of the shooting was on the stairs. I couldn't just lie there, I had to roll down. The tumble hurt a lot." On the day of the shoot, Donnie Yen Chi Tan was working on team B's action scene. on the set he ran into Cheung Hok Yau who was not in costume yet. Yen Chi Tan had no clue and asked Cheung Hok Yau, "Hok Yau, did you come to visit?"
Hok Yau's addition was so mysterious due to Hok Yau and director Chan Ho Sun's gentlemen's agreement. Hok Yau hoped that he would be able to help and thought a low profile would be good. Before the shoot, Hok Yau did not mention salary at all. After the shoot, Chan Ho Sun still gave him a laisee. Hok Yau insisted against accepting it and even joked, "Don't force me, I am very expensive! If people find out how would I dare to haggle with others next time!" Finally Hok Yau donated the laisee to charity, just as he said in the film. "Take from the people, use on the people."