Cillian Murphy enjoyed getting his fake nails into the role of transvestite Patrick 'Kitten' Braden in Neil Jordan's new movie, he tells Michael Dwyer, Film Correspondent.

Traditionally, when men have dressed as women in movies, they were playing for laughs. There have been some notable exceptions, most recently Cillian Murphy's remarkable transformation into transvestite Patrick "Kitten" Braden in Neil Jordan's film of Patrick McCabe's novel, Breakfast on Pluto. The movie is frequently uproariously funny, stamped with McCabe's anarchic humour, but it is just as often dramatically jolting.

The unplanned offspring of a priest (Liam Neeson) and his housekeeper (Eva Birthistle), Patrick Braden grows up during the 1960s in an Irish Border town, showing far more interest in wearing dresses and make-up than in football. Adopting the name Kitten, he sets off on a quest for his mother, setting in motion a series of misadventures through which he travels with the eternal optimism of Candide.

Born and raised in Cork city, where he switched from law studies to stage acting, Murphy attracted Jordan's attention with one of his first leading roles, as a suicidal young man in John Carney's Over the Edge (2000). "Neil asked me out to his house," Murphy recalled when we met in Dublin this month. "He talked about Pluto and asked me to read the script. I did, and I did a screen test. Then we both went off and did other things.

"When we made the film Neil was really focused. We did six days a week, 17 hours a day. Necessity is the mother of invention, so whenever the schedule was tight, he would come up with very clever ideas. We often came up with stuff on the spot because he trusted my instinct with Kitten. It was tremendously exhausting, and it was a bit of a party movie, too. We were on location all the time and there were a lot of late nights."

Murphy's marvellous immersion in the role of Kitten is so complete that it suggests a deep emotional investment in the character. "I only ever notice that retrospectively, usually when my wife tells me I've been acting like a lunatic," he says. "The thing about Kitten is that I fell deeply in love with her. I think every role affects you, but she is so open and transformative."

It's interesting, I note, that he refers to Kitten as "she". "I had to adjust to that from the beginning," he says. Getting Kitten's physical appearance right first involved a series of camera tests. "We had brilliant hair and make-up and costume people on the film," Murphy says. "Neil decided that she wouldn't smoke because it would draw attention to the masculine hands. We went for curly hair because it frames the face softer and it had that Marc Bolan look, that androgynous vibe. The clothes back then were very flattering to both men and women, so it was a perfect era to set it in.

"Neil has a great eye for things. In the disco scene he took red out of everything except the outfit Kitten is wearing. He kept adding ideas like that. One of the reasons I like working with directors who are so creative is that you can have complete and utter confidence in their vision. I would try anything for him."

That involved wearing women's clothes, shoes and make-up for most of his working days over two months. "The trick with that is a few gin and tonics, man, and off you go," he grins. "I spent a lot of time observing women as I went around London, on the streets and on the tube. I went out at night with some transvestites, and I was dressed as Kitten. That was the most rewarding time in terms of research. I realised how deeply vulnerable they are behind that ostensibly hard exterior that drag queens have. I could apply so much of that to Kitten because all she wants is to be loved and to look pretty."

Then he had to find Kitten's speaking voice. "I wanted to be feminine and flirtatious as much as possible," he says, "and to get that purring quality Kitten's voice has. My voice is pitched quite low, but some men I know have voices that are quite high." I mention that the Cork accent can be very high, even in some of the burliest Leesiders. "It can be," he laughs, "especially when they're being emphatic."

Reflecting back on making the film, Murphy singles out working with Liam Neeson, who plays his father, Fr Bernard. "For the big dramatic scenes with Liam, you really have to step up to the mark. When you act with Liam, something happens that transports you. It's strange. You're immediately in it. It's hard to describe, but you don't really feel like you're acting to each other. Those two big scenes with him at the start and the end of the movie, I just loved doing them. He's quite extraordinary."

Before Breakfast on Pluto, Murphy and Neeson had been in Batman Begins together. "We had no scenes together, but we had gone out at night," Murphy says. "Liam very sweetly rang and said, 'We're going to be doing these scenes together and I'm playing your Da, so let's go out', and we went out to dinner and on the lash. All those guys - Liam, Brendan Gleeson, Stephen Rea - they were all so supportive and helpful to me. Every week I was working with another really good actor, and that raised my game."

Having been a singer-guitarist with a Cork band in his teens, Murphy relished the scene where he performs a duet - dressed as a Native American squaw - with Gavin Friday on the Nancy Sinatra/Lee Hazelwood song, Sand. "Gavin just ate up that part and played it so tenderly," he says. "For me, as a frustrated rock star, it was just great. Any chance to get behind a microphone, I'll do it."

His touching portrayal of Kitten secured Murphy a Golden Globe nomination this month. "I'm delighted, but I'm just taking that with a pinch of salt," he says. "It will be nice to sit down with all these people I've admired for years. I am thrilled by it." As for the possibility of getting an Academy Award nomination next month, he just shrugs and says, "Why even bother thinking about something when you've no control over it?"

His hectic work schedule dictated that he "didn't have time to miss Kitten", as he puts it.

"Five days after we finished shooting Pluto, I was in LA, rehearsing for Red Eye. It was mad, suddenly having to play this killer and I still had my plucked eyebrows, curly hair and long fingernails from Pluto. When they saw me in LA I think they all got a bit of a shock."

A relatively low-budget thriller, Red Eye surpassed box-office expectations and gave Murphy his biggest US hit to date in a leading role. Murphy was born six days before Colin Farrell, in May 1976, but whereas Farrell shot from Ballykissangel into Hollywood leading roles with Tigerland, Murphy's career path has been more steadily, gradually upwards.

"You can't plan it," he says. "No actor can ever be the master of his own destiny or the architect of his own career. I've always tried to live by the words on the page. I read everything I get and I think I can tell what's good and what's not. It's important, too, to realise that even if you've got a tremendous director but the script isn't very good, it doesn't necessarily mean you should do that picture."

He revels in the variety of his work. When he finished Druid's Irish tour with The Playboy of the Western World - in which he was hypnotic as Christy Mahon - he took the boat from Inis Mór back to Galway, then flew to London and was playing the villainous Scarecrow in Batman Begins a couple of days later. "That, to me, is what acting is all about," he says. "You should try everything and not limit yourself, and if you want a long career you should do as many different roles as possible."

Post-Pluto, Murphy starred in Ken Loach's War of Independence drama The Wind That Shakes the Barley, which was shot in Cork this summer. "That was a beautiful experience," he says. "It wasn't like making a film. I saw no footage, no stills, no trailers. It was completely divorced from any experience I ever had making a movie. It was just this group of us on an adventure in Cork. The thought of it coming out as a cinema release seems strange because I haven't seen a frame of it."

This month he finished shooting Sunshine, his second film with director Danny Boyle and writer Alex Garland after 28 Days Later (2002). "I went straight from Ken's film into that. It's set on a spaceship 80 years in the future. I play a physicist. The sun is dying - which will actually happen at some stage. As in 28 Days Later, Alex can write a really good yarn but within that yarn he is commenting on society, and it works on both levels. The script for Sunshine is one of the strongest I've ever read. As Danny has done with other genre pieces, I think he's going to reinvent the science-fiction movie with this."

So it won't be like Star Trek? "Certainly not. Everything has been pushed so far in terms of special effects, but I believe you will still find new things in this. It was very nice to walk on set and see the flight deck and all the computer screens, and then to start pressing buttons and looking intelligent about it. That and Batman definitely brought out the little boy in me."

Now that he and his wife Yvonne have a little boy of their own - nine-week-old Malachy - Cillian Murphy is taking his first extended break in years. "I want to spend time with him. He gives me a whole new perspective on life."

Breakfast on Pluto opens on Jan 13

Boys will be girls Cross-dressing in film

I Was a Male War Bride (1949) - Cary Grant

Kind Hears and Coronets (1949) - Alec Guinness

The Belles of St Trinian's (1954) - Alastair Sim

Some Like It Hot (1959) - Tony Curtis, Jack Lemmon

Psycho (1960) - Anthony Perkins

No Way to Treat a Lady (1968) - Rod Steiger

Pink Flamingos (1972) - Divine

Thunderbolt and Lightfoot (1974) - Jeff Bridges

Rocky Horror Picture Show (1975) - Tim Curry

Tootsie (1982) - Dustin Hoffman

Kiss of the Spider Woman (1985) - William Hurt

The Crying Game (1992) - Jaye Davidson

Ed Wood (1994) - Johnny Depp

Hedwig and the Angry Inch (2001) - John Cameron Mitchell

Bad Education (2004) - Gale Garcia Bernal