By Caroline Briggs BBC News entertainment reporter

Breakfast on Pluto is based on Patrick McCabe's novel

Murphy's breathy portrayal of pouting transvestite Kitten has been lauded by critics.

He admits he was as "excited as a little girl" in the kitchen of his London home when he discovered he had been nominated.

"I was thrilled more than surprised," he said.

"I think this year has been quite interesting with films like Brokeback Mountain and Capote being nominated as well."

He will go head-to-head with Charlie and the Chocolate Factory star Johnny Depp - one of his favourite actors - for the same award.

I just want to make a piece of art and a film that affects people in some way Cillian Murphy

While Murphy is characteristically reticent about his chances of winning, he is excited by the prospect of being at the award ceremony in Los Angeles on Monday.

"I'm not in control of any of that stuff so I'm just going to go and enjoy myself," he explained.

"I'm just thrilled at the thought of being in a room with all these wonderful actors."

Tights-wearing terrorist

Breakfast on Pluto, directed by Neil Jordan, follows Kitten's picaresque adventures from his rural Irish childhood to 1970s London where he searches for his long-lost mother.

Murphy stars with Ruth Negga, Liam Neeson and Brendan Gleeson

The sweet, feminine boy encounters a glam rock band, a violent Womble, a Soho peep-show and is arrested as a tights-wearing terrorist when he is caught up in an IRA bombing campaign.

"Every actor wants these big transformative roles," Murphy said.

"I put my heart and soul into it. I have a deep, deep affection for the character and it had a profound effect on me."

Murphy spent time with transvestites in London while researching the role, but it was women who helped him capture Kitten's feminine charms.

'Observing women'

"I spent a lot of time observing women. Women have a particular way of carrying themselves and sitting, which is not a way I would do naturally.

"It's easy to do camp or 'Queenie' and it's a cliche too, so we were trying to avoid any kind of cliches and try to create something unique."

Murphy was so keen to play Kitten - or "Pussy" in the Patrick McCabe's book on which the film is based - he "pestered" Jordan for years.

Murphy said he had 'great affection' for the character

But he admits that, with hindsight, the role may have proved more difficult to pull off when he was 24.

"I started acting when I was 20, so I've been doing it for 10 years. I have learned a huge amount over the last five years so I hope I'm a better actor than I was five years ago."

When zombie movie 28 Days Later became a hit in 2002, Murphy was already hovering on the one-to-watch radar.

Scripts for films like The Girl with the Pearl Earring, Cold Mountain and Batman Begins followed, along with those for smaller, mainly Irish, films.

Murphy said it was a conscious decision on his part to choose a variety of roles in both arthouse and Hollywood-friendly films.

"Each one, you hope, makes you a better actor and you hope each one represents a big challenge.

'Plucked eyebrows'

"I think the more you work, the better you are. I didn't have any formal training so I have just been learning from working and watching."

Even last year's thriller Red Eye, which Murphy describes as a "popcorn movie", gave him vital experience.

"I think Red Eye is a very clever, entertaining film and, for me, it represented a challenge to play an American a leading part as an American."

Murphy said 28 Days Later was his 'watershed role'

Murphy actually filmed Red Eye after Breakfast on Pluto - an experience he said he found "difficult".

"I think it was about a week before I went to LA for Red Eye. I arrived there with curly hair and plucked eyebrows and I was supposed to be playing this killer. They were horrified by me!

"In the future I'm going to give myself more time to shake off characters before I step into someone else's shoes."

Filming on Ken Loach's The Wind That Shakes the Barley and Danny Boyle's latest film are already under the belt for Murphy and he says he would love to work with Jordan again "if he'd have me".

But he plans to take some much-needed time off before deciding on future projects.

"I can't really think about the future until I read a script," he explained.

"I just want to make a piece of art and a film that affects people in some way. That's all you can hope for really."