"Season of the Witch" is just one of several films that Irish actor Sheehan has been doing in addition to appearing in numerous TV programs. He is currently co-starring in the BAFTA-winning sci-fi TV series "Misfits," which is about a group of young delinquents who have superpowers. After "Season of the Witch," Sheehan’s next movie is the comedy "Killing Bono" (based on music journalist Neil McCormick’s memoir of the same title), which shows how Neil (played by Ben Barnes) and his younger brother, Ivan (played by Sheehan), were in a band together and, in their failed attempts to become rock stars, were overshadowed by four of their former school mates who went on to become the superstar band U2.

While Sheehan was in New York City to promote "Season of the Witch," I sat down with him for this exclusive interview. While chatting over tea at the Ritz-Carlton lounge in midtown Manhattan, Sheehan opened up about his hilarious experiences while filming "Season of the Witch," which superpower he would want the most in real life, and his fond memories of his "Killing Bono" co-star Pete Postlethwaite, who died of cancer just two days before this interview.

What was the toughest scene for you to do in "Season of the Witch"?

There were a few scenes I had to identify and isolate as important scenes to do with my character … this young acolyte guy who gets the balls of brass within him to follow the troupe across perilous Europe. So there’s a particular scene where they knock me off the horse, and they discover me following them. It was quite tough, because it was quite a surreal moment … It was quite scary. And so I think holding it together was the main challenge and being respectable and not shaking at the knees.

For a lot of movies that are serious in tone, I always hear stories that the mood on the film’s set was actually quite jovial. Was that the case with "Season of the Witch," and if so, was there a particular scene where you had to do a lot of takes because people kept laughing?

Every day! It was such a lovely unit. We were all away from home. We were all out of our comfort zone. We were all thrown together. We had a great laugh. There was a scene around the campfire where we’re all telling stories. None of us could keep a straight face. It all fell on Ron [Perlman, who plays Felson, Behmen's right-hand man]. Everybody else was shaking with laughter, and he was trying to keep it serious.

There was one point when Nic [Cage] was quite mad at himself. We were working for 13 hours straight, and it was nighttime, and it was a bit cold. And we all started laughing. And [Nicolas Cage] got quite angry at himself and said, "I’ve got to stop laughing!" And he put his hand in the fire! We were like, "What are you doing, man?" And he’s like, "The pain will help."

Did it work?

[He laughs.] No, it didn’t work at all. And it made me laugh more!

What was your audition process like for "Season of the Witch"?

It was a series of auditions. In the first two auditions, I stood in a little sweaty room with a camera with Elaine Grainger, who cast the film. She said, "Right! Put him there and him there. And imagine this. Here’s your sword." It was all very contrived because we had to do it within four bare walls. So the first audition felt a bit awkward; it felt like it didn’t go that well. And the second one felt a bit better, I thought, but I still felt pretty doubtful about it.

And then in the third audition, I met ["Season of the Witch" director] Dom Sena, and that went really well. It was at the third one, with the director there and everything, that’s the one that really worked for me, and that’s probably why I ended up getting the part, which was nice.

You had to do sword fighting in "Season of the Witch," and you had to play guitar for "Killing Bono." Which skill was harder to learn?

I would say sword fighting is physically harder, because you have that [sword fighting] choreography between me and Ron [Perlman] — we had to run that through from start to finish, and by the end, every time my chest would have to be beating but not heaving. I found sword fighting to be like a dance with a sword. So in that way, it’s probably easier, because it becomes fluid. And once it becomes fluid, it’s like riding a bike: You don’t think about it. You just go into the moves, and that’s it.

Whereas with playing guitar, I knew a little bit of guitar, but I’m absolutely not an intermediate player. I’m still a beginner. But I found it difficult when it came to things like kicking.

Have you seen "Killing Bono" yet?

Yes. I’ve seen it twice.

Since "Killing Bono" is based on Neil McCormick’s memoir, does the movie have a first-person, voiceover narration by the Neil McCormick character or is the story told strictly from a third-person perspective?

It’s third-person perspective. It starts out with him giving a very unstable account of why he’s in this very weird position where he’s gone mad. And then it goes back to [Neil and Ivan McCormick’s] earlier lives.

But it doesn’t keep referencing [the beginning of the film]. It just starts out at a late stage where it builds up to that point where he’s gone mental and gone murderous. And we build up that point showing their musical career or whatever you want to call it. But the film, for the purposes of drama, it puts forth this thing that Ivan was actually accepted into U2 … and Neil keeps it from him in a very sly way.

And in real life, Ivan was rejected by U2 after he auditioned for the band.

Right. And in the movie, Neil says, "No, my brother’s with me! He’s the lead guitarist with me and that’s it!" And eventually, when we’re doing well and our band’s career is picking up, it all comes to blows. So for dramatic purposes, that angle was put in. And so it becomes about these two brothers who hate each other and love each other. They can’t live with each other, and they can’t live without each other.

"Killing Bono" got a 15 certificate (which is similar to an R rating in the United States) mostly because of a particular sex scene with Ben Barnes as Neil McCormick. In the book, Neil talks abut having a lot of sex partners, so is the scene in the movie something that was in the book?

Yes. It’s the scene with the model he finds at a house party. It’s quite hard-on sex with a topless girl. Why is it always the sex and not the violence [that makes a movie get a stricter rating/certificate]? It’s strange. Like with "Blue Valentine." It’s a beautiful film.

They made the right decision to change the rating for "Blue Valentine" from NC-17 to R. There have been more explicit sex scenes in R-rated movies.

You know, the only scene [in "Blue Valentine"] I had to look away at was the abortion scene … with the needle. If it would be anything, I thought it would be that scene [that was responsible for the NC-17 rating]. But it wasn’t! It was the scene where [Dean, played by Ryan Gosling] goes down on [Cindy, played by Michelle Williams].

I know this is very sad to talk about right now, but what are your memories of working with Pete Postlethwaite in "Killing Bono"?

Just being star-struck when meeting him. "You’ve been in so many films of my childhood." It was such an honor. Pete was very ill when we were working together.

So you knew he had cancer when you worked with him?

Yeah, we knew, because I suppose he was getting chemotherapy at the time. And he was working around that as well, which is admirable. It was a great thing for him to keep working and making films and also trying to make himself healthy with the chemo, which is very, very hard on the system. It was a very surreal and strange and wonderful thing to be working with him, knowing he was sick and not knowing if he’d come through it, because the cancer was at a late stage.

Nick Hamm, who directed "Killing Bono," had been friends with Pete for 30 years. And on the last day [of filming the movie], Nick was crying and said, "I love you, Pete." He was one of the best actors to ever be put on this planet. He was an amazing, amazing fellow.

Ben Barnes gave me a sneak preview of the "Killing Bono" soundtrack when he played me songs from the movie. What do you think of the original music that was written for "Killing Bono"? And can you talk about your contributions to the soundtrack?

There’s Ben and his rock’n’roll voice. In fairness to him, I was blown away by the fact that he has a really great voice. He has a great, high-pitched rock’n’roll style.

One of the songs has my vocal, which I’m very proud of. It was written by Ed Kowalczyk [the former lead singer of Live]. It’s called "The Great Beyond." [Sheehan starts singing the song.] It’s a full-on rock’n’roll song. That came through Ian Flooks, who’s U2’s agent, who found this track and asked Ed Kowalczyk, "Can we use this track?"

So there’s a scene in "Killing Bono" with you singing lead vocals. It doesn’t seem like Neil McCormick would relinquish the spotlight over to his younger brother that easily to sing lead vocals on a song. Did that come about through some strife or was it an amicable decision?

It’s because strife, because Neil’s basically been turfed. That’s where it comes from. And the thing is, in the film, he’s been holding back slightly-more-innocent Ivan from being a rock star. And then he realizes that Ivan is a rock star already, and Neil’s just been trying to overshadow him and be his big brother. I’m the Edge to his Bono. He’s the one with the croons and the moves, and I’m the guitarist with not as much stage presence. That’s the dynamic in the film.

The relationship that Ben, the director and I worked out was that it would be like "Withnail and I," where you’ve got one guy [Neil McCormick] spinning off the planet, going: "It’s OK! We can get more money!" "What are you talking about? We’re broke!" And Neil is constantly pushing, "It’s OK! We can get a gig!" So Ben plays this guy who believes himself to be a rock star, and the rest of us are living on planet Earth going, "Look, Neil, just calm down! We’re not there yet!" So it was a nice kind of stubbornness, head-to-head, brotherly thing in the middle of it.

You’ve been really busy as an actor. When do you start filming the third series/season of "Misfits"?

I’m at a stage where we’re trying we’re make projects and "Misfits" all work together. The year is kind of chaotic at the moment. Hopefully, it’ll be in mid-May of 2011.

We left off with the "Misfits" characters at a crossroads where they can change their superpowers. Which superpower would you choose for yourself, if you could do it in real life?

It would have to be flight. If I could fly, I don’t think I’d be able to pass that up. The rest of them are quite anodyne: invisibility, etc. Flight just seems more magical or out-there. That would be one I have to choose.

Out of everyone in the "Season of the Witch" cast and crew, who made you laugh the most?

It would be Stephen Graham [who plays the con man Hagamar] or Nic Cage, but if I had to push to choose one, I’d probably have to say Stephen Graham, because he’s such a "Jack the Lad." He’s 100 miles an hour, all the time. He’s full of life and hilariously funny, but not trying to be. And Nic’s the same. He’s unintentionally funny. He finds the most bizarre and outlandish things funny. He made me laugh quite a lot, but in a different way.

You’ve been an actor for most of your life. What’s your earliest memory of wanting to become an actor?

I remember watching "Demolition Man" when I was about 9 or 10. Sylvester Stallone and Wesley Snipes! That film was way too violent for a 9- or 10-year-old to be watching, but I saw it when I was about that age, and I remember thinking "Whoa! These guys are such movie stars!" For a young lad, it’s always a real action-packed, shoot-‘em-up movie that kind of gets you.