For years, one of cinema’s most respected actors, John C. Reilly has lately blossomed into one of Hollywood’s funniest. “It’s all in the face,” the star of Cyrus tells Paul Byrne.

 There’s so much to like about John Christopher Reilly.

There’s the sterling work, of course, Reilly making such special early outings as What’s Eating Gilbert Grape? (1993), Boogie Nights (’97) and Magnolia (’99) all the more special. Reilly also took pretty decent offerings – 2002’s The Good Girl, Chicago, The Hours and Gangs Of New York; 2004’s Criminal and The Aviator; 2006’s A Prairie Home Companion – made them pretty near special too.

It was when this critically-acclaimed dramatic character turned his hand to balls-out-on-the-cymbal comedy though that John C. Reilly really began to register with the great unwashed. His loyal companion, Cal Naughton Jr., to Will Ferrell’s racing chump in Talladega Nights: The Ballad Of Ricky Bobby (’06). His thinly-veiled Johnny Cash troubled country star in Walk Hard: The Dewey Cox Story (’07). His childish step-brother to Ferrell’s childish step-brother in, eh, Step Brothers (’08). The man knows how to do funny. He just has to look like he’s not quite sure what his next line is.

“That is my technique, right there,” laughs the 45-year old Chicago-born Reilly. “It’s all in the face. After all my years of training, of doing my time in theatre, in support slots in movie after movie, I finally figured how to get my face on the poster. Look as dumb as possible.”

Having a face so Irish that it would make John Hinde swoon helps too, of course, and Reilly puts it to good use in Cyrus, playing sweet-natured John, the would-be suitor to hot mama Marisa Tomei’s Molly. The comedy comes into in the rather rotund shape of Molly’s son, Cyrus, who isn’t too crazy about having another man around the house.

PAUL BYRNE: In some ways, you’re in Step-Brother territory here again, with a cuckoo not wanted in the family nest. Only this time, it’s a stepson giving you all the hassle.

JOHN C. REILLY: Yeah, there are definite similarities, I guess, but the role is pretty different. I don’t play such an idiot this time out, I’m glad to say, and the rivalry has a different dynamic. There’s a lot of comic potential in this kind of conflict, and once you’ve got a love-hate thing going on, it can build and build into something you can really have some fun with. I laughed out loud when I read the script, and that’s pretty much my one true test when it comes to making comedies.

And when it comes to romantic comedies, I’m guessing the romantic element is helped more than a little by having someone like the lovely Marisa Tomei as your love interest.

Yowsa, yowsa. And what a great actress. You know it’s going to be pretty easy to pretend to love this woman because, you know, you do, instantly. Marisa just knows how to deliver, and it spurs you on. A real joy; acting is really all about the other person, in many situations.

The brains behind Cyrus, Mark and Jay Duplass, not only wrote your character especially for you, but they also encouraged improvisation on the set too. Easy to bring the John C. Reilly?

Very easy. Once I didn’t think about it too hard. Comedy has a lot of improvisation anyway, and it’s a very natural way of just finding the truth in a moment. You can just relax your mind and float downstream, so to speak. And it’s not like you don’t have a map at all. Mark and Jay wrote a beautiful script, and that makes it very easy to tap into. Shooting the movie pretty much in order help feed that organic process. The fact too that the left the dialogue blank for us was pretty inspiring.

It does seem as though you’ve embraced comedy of late. You’ve got still got drama roles, such as Larten in last year’s Cirque du Freak: The Vampire’s Assistant, but has comedy gotten a hold of your heart right now?

I think it does. A lot of that has to do with Will. The other person in these situations. The guy just makes me laugh, and somehow, I manage to make him laugh too. It’s pretty irresistable, getting to make a movie with that guy. It’s like we’re mitching off from making real movies, you know what I mean? It’s a case of, can we really say this? Should we take it this far?

It’s the little details that get me – cutting to Cal and Ricky in a bar, and Cal’s just dancing by himself as Ricky sits idly by.

It’s hard to keep a straight face when you get into that sort of silliness. Again, it’s just doing all the stuff that you would normally do if you were goofing around, waiting for the cameras to roll. That’s where the magic lies. And there’s an art to it, in that we give it a lot of thought. But it’s the spontaneity of this kind of comedy that gets me, and we’ll always let the cameras keep rolling as we riff on whatever comes into our heads. The main thing is, try not to laugh. Which is Catch-22, of course, because if it’s really funny, you’re going to laugh. And the stuff that’s really funny, that’s what we want to put in the film. Without the actor laughing at his own joke.

You started out in musical theatre, something that became pretty obvious with your Oscar-nominated turn in the musical Chicago – did you have a gameplan here? Had you got your heart set on being an all-singing, all-dancing, all-round entertainer?

I guess I did. But it was more that I just wanted to perform, and whether that’s through a drama, a comedy, a musical, it was all good to me. Early on, when I first started getting work in film, I was hooked by the whole process right from the start. I love the fact that it’s out there forever. That makes me try that little bit harder to do a good job; I don’t ever want to look back and see myself being lazy.

The rise from character actor to the guy on the poster – all good, or a tad difficult?

I couldn’t say it’s difficult, because the success means I get to make more of the movies I want to make. And I’m not such a face that I get all that much hassle on the streets. And when I do, it’s all positive. I don’t think I’ve made a movie yet where people felt their lives had been ruined, or that their nights had been wasted. So, yeah, no complaints here. Not yet, anyway.

We should ask about those Irish roots – the fifth of six children, born to an Irish-American father and a Lithuanian-American mother in Chicago, May 24th, 1965, you were brought up a good Catholic boy. And you’ve said you’d really like to play a priest. What went wrong?

Nothing too drastic – just the lure of showbiz. Which, when I come to think of it, is primarily the devil’s work, so, yeah, I think Father Ted and that crowd wouldn’t be too impressed. I do find the idea of playing a priest pretty fascinating though. Maybe one from the old country. I was over in Ireland, and had a ball. Feels like home, you know, but then, being a Reilly growing up in Chicago is like growing up in an Ireland theme park.

Words – Paul Byrne

Cyrus is in Irish cinemas from Sept 10th