JACK Black might well look more like a rumpled heavy metal fan than a Hollywood star, but the chunky Californian is certainly enjoying his "in-demand" status.

His busy schedule has seen him hit our screens in a glut of recent films, including School Of Rock, Envy and Anchorman.

Now, Jack's about lend his distinctive voice to the character of Lenny, a Great White Shark with a guilty secret, in the latest computer-animated DreamWorks comedy, Shark Tale.

Will Smith takes on the lead as the voice of Oscar, a fast-talking little fish with big plans, who gets into hot water because of a great white lie.

While Jack's character may seem fearsome by comparison, it soon becomes clear that this is one Great White who isn't quite all he seems. After all, there aren't many Great White Sharks who turn out to be vegetarian.

"He's a very sensitive and caring fish, and those are great qualities unless you're a Great White Shark," Jack smiles. "He has to hide it from his dad so he doesn't get kicked out the house."

The CGI creations reflect the appearance of the actors who play them and Jack does concede that his portly build may have inspired the his animated alter-ego - just a little.

"I've struggled with my weight my whole life. I'm doing the zoning thing where I cut out potatoes and bread," says the Los Angeles-born junk food fan.

"I don't think he looks like me, maybe they got my eyes. Mine are closer together, but they got the shape of the eyeball."

Voicing an animated film like this usually involves numerous studio sessions in front of microphone over a period years as the film is painstakingly constructed on computer screens.

Because of the absence of a film set, Jack didn't get to hang out with many of cast members, although he did get to share a studio with the fast-talking Will Smith.

"Every couple of months over two or three years you record a little more and I did work with Will."

However, the solitary nature of the job did ensure Jack got his share of the limelight.

"I like going it alone, because then it's all about me, buddy, me!"

He's also thrilled to be sharing the credits with a cast of bona fide Hollywood superstars, particularly the legendary Robert De Niro, who voices Lenny's Great White dad, the distinctly Godfather-esque Don Lino.

"I'm just stoked that these cartoon characters are having a scene together. That's good enough for me. I like that there's a poster that says De Niro and Jack Black."

It was John Cusack's High Fidelity, based on the Nick Hornby novel, that really got Jack noticed in 2000 after eight years in small roles. From there he stepped up to be a leading man in the Farrelly brothers comedy Shallow Hal, with Gwyneth Paltrow.

Without possessing the classic good looks of Hollywood's usual leading men, the unassuming actor never expected to become a star.

"I'm no Matt Damon, I wanted to be a character actor. I never thought I'd get leads the way I've been able to," he admits.

His next project is another step up for the hard-working actor. He's currently down in New Zealand with Naomi Watts and Adrien Brody in Peter (Lord Of The Rings) Jackson's 200 million dollar remake of King Kong.

Jack will play a movie producer who captures the giant ape and makes him a freak show attraction. He's also set to star in Michel Gondry's forthcoming sci-fi thriller, Master Of Space And Time.

Hollywood has taken its time to recognise his talents, he says.

"The problem was, they didn't really know what to do with me. School Of Rock is the closest anyone has come to putting the real me on screen."

In fact, the real Jack also fronts his own heavy metal parody band, Tenacious D, with old friend, Kyle Gass. The duo have acquired a cult following with their unwavering dedication to old-school rock, and Jack's certainly not shy when it comes to describing their unique sound.

"If Beethoven and Bach hooked up with Mozart and made a band, they could be a distant runner up to The D," he explains proudly - with only a hint of irony.

Considering Jack's Hollywood status and love of all things rock, it would be easy to assume he's a hellraising party animal. In fact, Jack's personal life couldn't be more different. Having dated partner Laura Kightlinger, a comedy writer on Will And Grace, for several years, the actor says he actually likes to keep a low profile when it comes to the famously excessive celebrity party scene.

"It's kind of a drag when people want to party with me because they think that's what I'm gonna love. I deal with it by walking away slowly, smiling and waving.