"[KATO] ALL ASIAN ETHNICITIES, Male, 20s-early 40s. Britt Reid's manservant/chauffeur by day and Green Hornet's martial arts-skilled sidekick by night sptv050769. Actor doesn't have to have martial arts experience."

Above is the casting call that spells doom for Stephen Chow's plans to star as Kato in Michel Gondry's The Green Hornet. After originally being set to direct from a script by Superbad's Evan Goldberg and Seth Rogen, who is also starring as the masked crimefighter, Chow now looks likely to have nothing to do with the project whatsoever.

"There was a mutual and amicable decision by both sides to move on," Sony said in a statement. "We are out now to cast a new Kato and remain fully committed to Michel Gondry's exciting vision for the film, which will begin production this September."

All of which sounds like platitudes of the highest order. So what is really going on with The Green Hornet? Rumours have been flying around, from a simple scheduling conflict stemming from Chow's interest in another role, to the suggestion that the Hong Kong-based actor and Gondry had very different ideas of what to do with the former radio serial. No one knows exactly what went wrong, but it's not hard to guess.
For a start, Chow's move from being the guiding light to a sidekick role, with somebody else taking over the reins, must represent a dent to the ego, even though the actor isn't known for hissy fits. One can only imagine that whatever impasse caused his exit must have been pretty severe: the appointment of the star and director of Shaolin Soccer and Kung Fu Hustle to the role made famous by compatriot Bruce Lee created a huge buzz in the blogosphere when it was announced. It will be almost impossible to replace him with a candidate of similar standing: there just isn't a well-known (in the west) actor of similar ethnicity with the right mix of comedic and martial arts nous. One wonders whether the casting call details, which make clear that fight skills are not necessary, suggest that an unknown is now being sought.

The Green Hornet still - just about - looks like an attractive prospect, and its box-office clout will be helped if Cameron Diaz agrees to take the female lead. But you have to assume that Goldberg and Rogen had written a pretty big role for Chow, a superstar in China, which suggests that an actor of considerable screen presence will have to be drafted in to replace him. The ebullient Rogen also needs a strong foil to play off - he's at his best when operating as part of a talent-packed cast. And all this, lest we forget, has to happen before September, when the film is planning to shoot. Frankly, it's not looking good.

I'm still intrigued, however, to see what Gondry has in store. The Eternal Sunshine of the Spotless Mind director has talked about introducing a new technique for the action sequences that sounds like post-Bullet Time eye candy. The Frenchman has an eye for visual flourishes that is almost unmatched. If his ideas for the film led to the falling out with Chow, let's hope he's going to bring something spectacular to the table to make up for it.

There hasn't really been a successful comic-book movie with a comedic approach since ... well, can you remember one? So The Green Hornet is flying into uncharted territory. It's the usual dilemma: camp it up too much and the audience no longer feels concerned about the welfare of the protagonists; take things too seriously and there isn't a lot of point having an actor like Rogen in the lead. Plus, every critic under the sun accuses you of having Dark Knight syndrome.

Rogen and Gondry certainly have the chops to turn around the current penchant for moody superhero movies without lapsing into facile Joel Schumacher territory. There ought to be a sweet spot in between the high camp of Batman and Robin, or the ill-fated The Spirit and the furrowed brow of Christopher Nolan's rather stern Batman films. Can they find it? First of all, they need to track down their Kato. Who would you cast, and where would you take the Green Hornet? Do you still think the creative team can pull this one off? Answers below, please.

Meanwhile, we've got a treat coming up for you next week from a movie that I rate as the top comic-book adaptation of 2009. Watchmen is on its way to DVD, and we'll be bringing you the first five minutes on the site, together with an exclusive video introduction and interview with director Zack Snyder, who talks about the challenges of bringing the greatest graphic novel of all time to the big screen. Make sure you check back here at 23:55 on Monday.