Running through walls, controlling minds, seeing the future. It's all in a day's work for the New Earth Army branch of the American military. Right after breakfast, and killing goats by staring at them. Mildly confused? It's no wonder; Grant Heslov's film, a fictional adaptation of Jon Ronson's non-fiction novel, is a barmy, wacky beast.

So how do you go about making such a manic movie? Luckily, director Grant Heslov, author Jon Ronson, George Clooney, Kevin Spacey and Quentin Falk were on hand to answer such questions.

Given the non-fiction, absurd nature of the material, how did you approach the film? Was it hard to judge the tone?

GH: Well, myself and George read the tone in exactly the same way. And everything, the production design and so on, had to support that tone.

GC: I think the documentary hit the right tone as well. It was actually floating around for quite some time as one of those great un-made screenplays. We were anxious to get our hands on it.

What did your military consultant make of the movie's content?

GH: He was quite surprised! No, he actually loved it – he had a really great sense of humour.

Did you practise at home to get your psychic powers ready for work?

KS: Well, I ran into a lot of walls in Puerto Rico… [Laughter]

GC: It's funny, really, because we did make up a few of the bits, but some of the wackiest stuff – like the walls – was completely real. They actually tried to run through walls.

JR: The physics of it was incredible. They believed that atoms were mostly made of space. And seeing as humans and walls were mostly made of atoms, they thought they could kind of… merge. The key word there is “mostly”. [Laughter]

Jon, how do the characters compare to the real-life people you met?

JR: Oh, George’s character is based on 4 or 5 different people put together. But Jeff Bridges is absolutely correct – right down to the appearance and how he sounds and everything. Like trying to be invisible, but then downgrading it just "not being seen"... There was even a guy I met who did show me a video of his hamster being stared to death. It went down, then got up again at the end. So it was an inconclusive snuff video at best.

So did you approach the characters as real-life people, or start straight from scratch?

KS: Well, it’s all in the script. For some projects you have to be accurate, almost an imitation of someone, when the person you're playing actually lived and is well-known. But no-one knows who these guys are so we could just do what the hell we wanted!

GC: Unlike, say, Good Night and Good Luck, where we had to be accurate about everything, here we could do whatever and just have fun.

What was it like working with Ewan?

GC: After the restraining order, it was very hard to work with him… [Laughs] No, Ewan is a really normal guy, fun to work with. He’s completely professional, so he’s done all his work before he turns up on the day, so you can just enjoy the rest and have fun.

They say never work with children or animals. How were the goats?

GC: First I was a fox, now I’m with goats… No, this goat was a particularly nice goat. He was a really good actor – he came in and just stared at the camera and was like *does a goat noise* If only Ewan could do that...

Do you actually believe in psychic abilities?

GH: I’m quite open-minded about it all; I think some people are naturally more psychically… aware than others.

JR: I, on the other have, have a completely different view. I think it’s all completely nuts.

So have any of you had any paranormal experiences?

KS: Working with you, George, is as paranormal as it gets.

GC: I’m not really a big believer in that stuff…

George, you and Grant go way back, you've worked together a lot, so on set, who's the boss?

GC: Grant has comprising pictures of me from 1972, so he’s very much in charge. He’s the boss. I have nothing but faith in the guy – I’m very lucky to be his friend.

Kevin, you’ve taken a break from leading roles in films recently and done lots of theatre work – are you just waiting for the right script to come along?

KS: Well, I did three movies last year, two the year before, and two the year before that. What break are you talking about exactly?! Oh, you mean actual lead parts? Well, I’ve just made two films in which I was the “actual lead”, but I’ve been focussed on building up the theatre company over the last 6 seasons. It’s going very well – my priority will continue to be the Old Vic, and I do films when they suit my schedule.

Check out the suave Mr Clooney in action on the carpet over here. And no, we don't have pictures of goats.