He just knows how to play the part.

Cillian Murphy has a very useful skill for an actor—he knows how to disappear. Frances McDormand, one of his favourite movie stars, can do it too. They both have invisible drapes, to be opened and closed at will.
In the crowded bar of Edinburgh's Traverse Theatre, fiddling with his cell phone, Murphy wears a jacket several sizes too large—he looks more like a vitamin-starved student than the zombie-slayer he played in 28 Days Later... Then he pushes back his greasy coif of hair and turns up his pellucid blue eyes. The result is instant movie star: I stop worrying about whether he has eaten lunch and ask when he is moving to Los Angeles.
"I couldn't live in LA," says Murphy, with a look that says the drapes are closed at the moment. "I don't understand it."
The effect is deliberate; Murphy, who is comfortable in so many different stage and screen roles, is very uncomfortable playing the star. Of being on the press junket for 28 Days Later..., he says, "You forget the meaning of words because you've said them so often. I find myself deliberately trying not to be engaging."
At 28, Murphy has a good deal to be disengaged about. He ditched his law degree after starring in the universally acclaimed stage play Disco Pigs, at the Edinburgh Fringe Festival in 1997, and decided to become an actor. Six years—and many roles—later, he's back in Edinburgh, at the International Festival, playing Konstantin in Peter Stein's production of Chekhov's The Seagull. The gaps in his theatrical education have been filled in while on the job.
"I never had any burning passion to be an actor—until I actually started it," he says in his natural accent, as straight out of Cork, Ireland, as a pint of his namesake stout. "I acquired it as I went along. I don't have any preconceptions, I don't have any baggage."
Murphy had neither read nor seen The Seagull when he accepted the part of Konstantin. He had not heard of Peter Stein, who he now describes as "the fucking German uberdirector."
If Murphy sounds flippant, it's because he has opened the drapes a little. He takes the technicalities of acting seriously, preferring British theatre's discursive approach to the Hollywood mode—a process that requires sitting in the trailer for eight hours, then coming out and following the director's instructions. And while some agents would be urging an actor with Murphy's cheekbones to go all out for the romantic leads that Colin Farrell can't manage, his people understand that he needs to go back to Dublin for Juno and the Paycock.
"In film and TV, you spend a lot of time waiting around, with a lot of people waiting on you," says Murphy, forgetting, for a moment, to be disengaging. "And there's not a huge amount of thinking about the actual craft, and honing that craft. Whereas in theatre, from day one, you're in there talking about this part, working with it, improvising—that, for me, is essential. Some actors can just turn it on, but I need a bit of groundwork."
In spite of his preference for the stage over the screen, Murphy says it's an exciting time to be making movies. He enjoyed Paul Thomas Anderson's Punch Drunk Love so much that he watched it twice in one sitting. David Fincher and Wes Anderson, as well as the Coen Brothers, Terry Gilliam, and Robert Altman are all on his wish list of directors to work with.
As for roles, Murphy aims for variety over conformity, choosing roles that will stretch him each time. "I'm not snobby, but it has to have some validity for me," he says. "I want to be involved in movies that have integrity, that make an impact."
To that end, he is as comfortable playing a butcher in 15th century Delft, in Peter Webber's forthcoming adaptation of Tracy Chevalier's Girl With a Pearl Earring, as he is playing a small-time bad lad in the Irish thriller Intermission, alongside the ubiquitous Farrell. In the theater, he has his eye on one of the definitive roles in the Celtic canon: Christie (sic) Mahon, in John Millington Synge's Playboy of the Western World. He also sees no good reason why Hamlet should not have Cork connections ...
"Just because I'm Irish, my extraction should dictate what roles I can play?" Then, realizing how comical this sounds in his straight-off-the-boat brogue, Murphy gives a look that says the drapes may close at any moment, and offers, "Diversity is the only thing I insist on—I don't want to have a career path; I want to have an interesting career."