Chapman To faced many difficulties when acting in his new film Naked Ambition 3D.
According to an article in Hktopten, he had lost 20 pounds while filming the movie.
In addition, he had to call in many favours and had asked Charlene Choi and Sandra Ng to be guest stars in the film.
He said: "Charlene was the first female artiste to raise her hand and say she will help, but because she was too artistic (acting was flat), not everyone knew how to appreciate her acting.
"Thus, I had a headache at first, but in the end I took care of it."
Charlene has also admitted to having some difficulties acting sexy for the role.
Previously, it was reported that she pouted and pretended to act sexy but her co-star Chapman To merely glanced coldly at her.
As for Sandra Ng, Chapman revealed that she was very loyal and did not ask about the salary when she agreed to be one of the guest stars.
Photos in the gallery below feature snapshots of Charlene Choi.