Perhaps surprisingly, for one blessed with chiselled good looks, a steady gaze and unassuming charm, Murphy first came to public attention for his performance as a character called Pig.
He brought an intensity and depth into the lead role in Enda Walsh's intense and compelling 1996 play, Disco Pigs, that captured the attention of Kirsten Sheridan, and led to him being cast in the same part in the movie version of the play.
Released last year, the project came as a welcome antidote to the spate of trashy teenage dramas burdening our screens prior to its release. Sheridan's imaginative direction merged fantasy, harsh reality, tenderness and disturbing obsession. But even without it, Murphy's performance alone was worth watching the film for.
Since his stage debut, he has appeared as Claudio in Bickerstaff's open air production of Much Ado About Nothing; he has played Curley in The Country Boy and Johnny Boyle in Juno and the Paycock, both of which were directed by Garry Hynes.
His film and television experience includes John Carney's On the Edge, The Trench, Sweety Barrett, Sunburn, How Harry Became a Tree, and The Way We Live Now for the BBC—in which, Murphy tells me in a posh English accent, he played "an English gent of some description."
"I know this might sound really boring, but I find film and theatre equally exciting. I really do," he says. "The opening night of a play, for instance, is much scarier than a film premier (sic). When the film is done, you can't do anything about it. It's terrifying getting up in front of a live audience. But the terror of theatre is great. You get an amazing rush from it. That immediate response you get from an audience in theatre is really special. There's nothing like it.
"Even before I got into acting, I always loved the magic of film. I love the way film can create a whole world. It takes acting in a few films to find your feet, though. As far as acting in both goes, you learn a lot faster and more intensely in theatre," he says snapping fingers on both hands.
"But doing it for film is very much about acting in the moment. It's so stop-start. And you get a few goes if you're not happy with the way a scene went."
Our interview is squeezed in between rehearsals for his latest play. Neil LaBute—whose interesting and very black film, In the Company of Men, was either loved or hated by critics, and whose Bash enjoyed a well received run at the Gate last year—has written The Shape of Things. It focuses on art, relationships, and what lies beneath them, seen through the eyes of two American couples. Tight-lipped about the story because of its twist, Murphy reveals only that it's quite dark, it's funny, and in it he plays "a sort of a geek."
The first time he got a feel for acting was during a drama workshop in fourth year in school. "I happened to meet Pat Kiernan who ended up directing the play, Disco Pigs. He came to our school for this workshop and it was great fun. That started me going to see other shows. I was really into music, though. I never saw myself then as an actor."
Playing guitar with a band was Murphy's first stab at performing live. "Sons of Mr. Green Genes was our name," he admits, blushing, "which we nicked from a Frank Zappa song."
So, to what does he attribute his versatile talent, both in front of a camera and on stage? "The whole thing is so collaborative between the director, the writer, the other actors. I think a lot of it comes from instinct though, as well. The director guides you in certain directions, but hopefully the actor already has an instinct that can be relied upon. Also, you need to have the courage to try things and for them not to work. You have to be able to learn from your mistakes."
His other inspirations come in the form of the young Al Pacino, Philip Seymour Hoffman (Happiness, Boogie Nights, The Talented Mr. Ripley), and Brendan Gleeson (The Field, The Butcher Boy, The General), with whom he has just finished working on a new film, 28 Days Later...
In it, he plays someone who wakes up from a coma in "a sort of post-apocalyptic London." After that, there's a role in Intermission, a new film by playwright Mark Rowe (sic) (who wrote Made in China) which is, according to Murphy, "a far cry from any sort of twee Irish film."
One stage-to-screen leap he won't be making, though, is for a role in the film adaptation of LaBute's The Shape of Things, directed by Danny Boyle, which is due out in October this year. "I think they've already cast a crowd from London for the film," he says.
Despite the increasing critical acclaim surrounding his versatile acting abilities, Murphy's feet are planted very firmly on the ground.
"I just try to give the piece as much as I can to the character. I try to invest in it totally and to do justice to it in every way. If someone has created a well-drawn character, then I think the least that should be expected from me is to give it as much as I can."
Well, you can't ask for much more than that.
The Shape of Things will be showing in The Gate, Dublin for three weeks only, from February 5–23.
Cillian Murphy isn't your typical thespian. Very laid back, with no delusions of grandeur, the Cork-born 25-year-old had no formal acting training. He confesses to loving every aspect of the job, but believes there are more important things in his life than getting a part. "I just do what I do for a living," he grins.