Attention, people of Earth: If Zaphod Beeblebrox, President of the Galaxy, seems familiar to you, that's because he's based on several of what you would call "celebrities."

"I pushed for an Elvis/Freddie Mercury vibe," says Sam Rockwell, the actor who embodies the far-out prez in the current hit film, The Hitchhiker's Guide to the Galaxy. "There's also some Vince Vaughn in there — Vince does a great Elvis — and Bill Murray from Kingpin."

And in case you're curious, yes, Rockwell also modeled his performance on several real heads of state. "I watched Bush and I watched Clinton," he says. "I was actually pretty nervous during rehearsals because they asked me to tone down the Southern accent."

It was Rockwell's versatility that won him the part of Zaphod. He originally auditioned to play the less flamboyant Ford Prefect, a role that later went to Mos Def. "I read for Ford and then I heard that Mos was cast," he remembers. "After that, I heard that Will Ferrell or Jack Black was doing Zaphod and then the whole project went away for a long time. Then I heard that I had the part! I didn't know what they wanted so I went in to meet with them again. My girlfriend at the time said I should do the Vince/Elvis thing and they liked it. Then I started throwing in the Clinton and Bush stuff and they really went for it."

Surprisingly, Rockwell had never read Douglas Adams' novels before stepping on to the Hitchhiker's set. Even now, he admits that he's only read the first installment of the five-book series. Nevertheless, his performance has been singled out by fans and critics alike as one of the best things about the movie. That comes as a big relief to Rockwell.

"I wasn't sure if it was going to work," he says. "People were nervous about the whole Clinton/Bush/Elvis/Mercury thing. I was like, 'I got to do my thing here.' Fortunately, [the director] Garth Jennings trusted me and let me go. And the movie as a whole is really fun. There's some amazing stuff in there. I love the dolphin bit at the beginning and the Guide itself is great. It almost steals the movie."

Rockwell's next project is in a decidedly more dramatic vein. He's one of the impressive list of actors — including Jamie Foxx and Peter Sarsgaard — who will be appearing in Sam Mendes' Gulf War drama Jarhead, which comes out this fall.

"It's hard not to get typecast in Hollywood," he says. "I'm trying to avoid that, because I want to do a lot of things. I know what I'm capable of and I forgive them because they don't know that yet. They haven't seen me play Hamlet. They're not going to just cast me as an English aristocrat. I'm going to have to prove that on my own. That's OK — that's what you have to fight for if you want to be an artist."