BATTERY PARK, N.Y. — You don't interview Sam Rockwell as much as you stand back and watch him perform.

During interviews in New York City to publicize his new project, the science-fiction comedy "The Hitchhiker's Guide to the Galaxy," the 36-year-old character actor preferred to stand rather than sit in the chair provided for him.

He then proceeded to do impressions, cracked a few jokes and riffed on the state of the movie industry and the progression of his film career, rather than providing answers to the questions asked by a roomful of journalists.

"You don't mind if I just sort of say a few things off the top of my head, do you?" he asked the interviewers who were lucky — or unlucky enough, depending on which one of them you ask — to have witnessed Rockwell's impromptu, 25-minute "set."

From there, it took several minutes just to steer him onto the subject of the film, in which he plays Zaphod Beeblebrox, the two-headed, three-armed President of the Galaxy, who's on the run after stealing an experimental spaceship called the Heart of Gold.

"That's probably what you're here for. You want to know what being in the movie was like, right?" he deadpanned.

According to Rockwell, he originally auditioned for the part of Ford Prefect, an extraterrestrial journalist and best friend of the movie's main character, Arthur Dent. (That role went to rapper-turned-actor Mos Def.)

"I met with (the producers and director Garth Jennings), and they pretty much told me I nailed the audition," Rockwell recalled. "And then I didn't hear from them again for a while, so I figured I was out of the running.

"When I finally did get the call-back, they asked me how I saw Zaphod and how I imagined playing him," he continued. "It was weird. I suddenly felt like I was auditioning all over again."

Still, Rockwell managed to put his unique stamp on the character, which he based partly on an impersonation done by his friend, actor Vince Vaughn ("We call him Vince Elvis," Rockwell said), as well as Bill Clinton and President Bush.

He also threw in some Gary Busey for good measure. "Gary is pretty much the craziest guy in the world. You don't know whether to be scared or amused by him, whether to think he's a genius or an idiot, which is what I was going for," Rockwell said.

As complicated as that sounds, he also had to perform with a prosthetic second head and third arm, which, he said, "looks like a lot more fun to do than it really is."

"The worst part is trying to stand still in front of a green screen, which is really difficult when you're trying to stay in character as this completely whacked-out guy."

Rockwell regrets that the film didn't give him much of an opportunity to interact with his "GalaxyQuest" co-star Alan Rickman, who provided the voice for Marvin, a depressed android character. "Alan was off in a studio somewhere. We never got to see him," he sighed.

Still, the role provided Rockwell with plenty of opportunities to make his co-stars — and audiences — laugh. "So at the end of the day you can't really say that it was too bad of a job," he said.

And he's excited that the movie is providing him with what's arguably his most high-profile role to date (he's previously appeared in "The Green Mile" and "Matchstick Men" and played former game-show host Chuck Barris in "Confessions of a Dangerous Mind").

Rockwell will appear next as the title character in an adaptation of P.G. Wodehouse's "Piccadilly Jim," opposite Frances O'Connor, Brenda Blethyn and Tom Wilkinson. "It's as different from this movie and this part as it can possibly get," he said with a shrug.