Athena Chu, like Chow, acts in two previous installments.

Lau says the latest will provide answers for some of the unsolved puzzles from the first two episodes.

He says it took a lot of persuasion to get both Han and Tang to join the cast of the film. He waited for eight months for Han to agree.

Revealing why he took his time, Han says: "I was reluctant because I felt huge pressure.

"It will be really difficult to improve on a role that has been perfectly played by Chow before. Inevitably, I will face comparisons, but none can finally refuse to play their childhood idol?"

But Han seems to have made an impressive start. He lost 8.5 kilograms within 21 days while preparing for the role.

Lau dismisses Han's fears about comparisons.

"Han and Tang are to play Joker and Zixia, not Chow and Chu," he says.

"Many actors play the same Hollywood superhero in different movies, so why do we have to stick to one cast?"

He says the third installment aims to attract young moviegoers with newer elements, and adds: "Due to the lack of special effects 20 years ago, many scenes could not be realized then. But now I have the opportunity."

The earlier films were about the failed romances of Monkey King and Joker with several women.