Scooby-Doo’s two-legged friend

“As an actor you are always hustling for a job,� says Matthew Lillard, whose hippy-dippy performance as the beatnik Norville “Shaggy� Rogers was the saving grace of the mystery-comedy “Scooby-Doo.�

The 2002 hit film was based on the beloved Hanna-Barbera cartoon series about a timid Great Dane and his four human friends who solve mysteries.

“Your life is about selling yourself,� says Lillard, who is friendly and talkative despite battling the stomach flu. “There are sellers and buyers, and I am a seller.�

But for now, he can cool it on the sales front. “Everyone is, like, we should wait ... with three great movies maybe the climate will shift a little.�

Lillard certainly has a lot on his plate this year. The sequel “Scooby-Doo 2: Monsters Unleashed� opens Friday, and his role as the computer-generated Scooby’s best friend has been beefed up considerably from the original.

He’s about to start rehearsals in London for the West End production of the play “Fuddy Mears,� which will keep him in England for four months. Lillard also has two more films scheduled for release this year: “Without a Paddle,� in which he actually gets the girl, and “Wicker Park.�

Even though the lanky, dimple-cheeked Lillard has appeared in more than 30 films, including “Serial Mom,� “Scream� and the indie fave “SLC Punk,� he still feels like an outsider.

“It’s hard to find your place in this town,� says the 34-year-old. “It’s hard for them to give you your break. Johnny Knoxville comes on board and somebody slaps him with the moniker ‘superstar.’ I am not saying he’s not. He’s obviously a good-looking guy and he’s funny. He’s great, but if you don’t get that slap early, it’s hard to fight up the ranks of Hollywood leading guy.�

Raja Gosnell, who directed both “Scooby� movies, says Lillard is so in sync with his character it’s as if he channels Shaggy on set. “He’s an actor who is totally willing to try anything,� Gosnell says.

“We will sort of have a set plan in terms of what the blocking and staging are, but I just basically turn on the camera, let Matt go and let him be Shaggy. He is always looking for another joke. I love that about him. It’s like having another director on the set. There are his ad-libs in the film and staging.�

Lillard, who has been artistic director of two theater companies and studied at the American Academy of Dramatic Arts in Pasadena and at Circle in the Square in New York, prepared for Shaggy as seriously as if he was portraying “Hamlet.�

“It’s a hard character,� he says. “When you do someone like Shaggy everyone has an opinion. You know that old expression, ‘You can’t please everyone all the time.’ �

Including the cartoon version of Shaggy. In last year’s live-action/animated comedy “Looney Tunes: Back in Action,� Lillard has a cameo in which his animated counterpart tells the actor everything that was wrong with his performance.

Because Scooby is computer-generated imagery, Lillard must do all his scenes with the pooch reacting to nothing.

“Have you ever had an honest moment with nothing?� he asks. “It’s so weird. The hardest thing is when you’re carrying him, holding him, running with him and being tackled by him. It’s all imagination. You have to create a relationship. He’s your best friend. You have to be Abbott and Costello.�

He has had invaluable help from Neil Fanning, an Australian actor who is the voice of Scooby.

“He’s off-camera and I have a mike in my ear. And if he can, he’s in my eye line. I couldn’t do it without him there.�