Peter Pau, credited as one of two directors for the action-fantasy film Zhong Kui: Snow Girl And The Dark Crystal, was never hired for the part.
The 62-year-old Oscar-winning cinematographer of Crouching Tiger, Hidden Dragon (2000) was the film's producer, cinematographer and head of visual effects. But he ended up aiding the original director Zhao Tianyu so much that he was given co-director credit as well.
Pau explains: "Zhao Tianyu is a great director, but he had had experience making dramas only, not action or big fantasy movies such as Zhong Kui. So I decided to help him as much as I could during the shooting and in post-production.
"I was the producer after all and I really needed to make sure that the film would be completed in time, so I thought I'd just step in and help out," he tells Life! in fluent English over the telephone from Hong Kong.
Eventually, the film's executive producer Ann An decided to make him director as well.
Pau recalls: "She said to me, 'Peter, you worked so hard, so you should also be director.' What could I say, right? I was like, 'Oh, okay.'"
What did Zhao have to say about the decision?
Pau laughs and says: "Well, even if he minded, he couldn't do anything about it. That's Ms An's decision and this is really her movie."
The film, which stars China A-listers Chen Kun and Li Bingbing, tells the story of the mythological figure Zhong Kui, a demon slayer known to be fierce and righteous.
In this version of the story, Zhong Kui (Chen) falls in love with a beautiful demon (Li) and is torn over whether to kill her. The film opens in Singapore tomorrow.
According to Pau, Ms An had all along intended to make it a "Chinese superhero movie" and Chen came on board because he was "absolutely fascinated" by the legendary figure.
Pau himself makes a tiny cameo towards the end of the film as the Heavenly Emperor.
He says with a chuckle: "Again, this is Ms An's doing. She and director Zhao were looking for big stars to play this tiny role, but either no one could make it or there wasn't enough time.
"So they made me do it. I said okay, but only if they made me really tiny. I'm not narcissistic and I'm no actor."
What he is, is the son of the late famed actor Pao Fong (Year In, Year Out, 1995) and the younger brother of Golden Horse-nominated actress Paw Hee Ching (Rigor Mortis, 2013).
"My father started taking me to the film set when I was a child, so I knew a lot about that world. But I was never interested in acting.
"I don't think I can do it and I don't enjoy it either, even though I know being an actor can earn you lots of money," he says with a laugh.
Instead, he found his calling behind the camera and chose to pursue a film-making degree at the San Francisco Art Institute.
He returned to Hong Kong in 1986 and has since been the cinematographer and producer of more than 30 films, many of which earned him major awards, including six Best Cinematographer nods at the Hong Kong Film Awards and a Golden Horse (Perhaps Love, 2005).
The biggest accolade in his career to date is obviously the Academy Award for Lee Ang's wuxia flick Crouching Tiger, Hidden Dragon, which was "a huge honour and huge encouragement" for him to "keep doing what he loves".
The Oscar drew many Hollywood scripts his way, but he was not particularly interested in many of them.
Shoot 'Em Up, a 2007 actioner starring Clive Owen and Monica Bellucci, was one of the few Hollywood offers he accepted.
The industry's genre films, he says, are too specific and cookie-cutter in nature.
"In Hollywood, the studios have a very set idea of what movies should look like. If it's a comedy, it should look one way, and if it's a horror film, it should look another way.
"As the cinematographer of those kinds of films, you can't express yourself freely. I would rather work in China, where the cinematographer can work with the director in deciding what the film should look like, rather than have the studio on your back."
Despite the accidental director credit for Zhong Kui, he would, in fact, like to call the shots on a movie set more often.
Pau, who has also directed The Touch (2002), an action drama starring Michelle Yeoh, and Misty (1992), a romantic drama starring Tony Leung Ka Fai, says: "I'm someone who puts myself in the whole project and I always do my best.
"I'm 62 years old and I don't know how many more years left I have in this industry. But as long as I'm here, I hope people will remember me as someone who wholeheartedly contributed everything he possibly could to the film industry."
Follow Yip Wai Yee on Twitter @STyipwaiyee
Zhong Kui: Snow Girl And The Dark Crystal opens in cinemas tomorrow.