I've always fondly imagined the Pixar studios to be a fun Silicon Valley computer company crawling with unspeakable wonks and geeks, and meeting Pete Docter does little to disabuse me of this notion.

Very tall and suspiciously boffinish, the man behind Monsters Inc and the WALL-E story looks like he should be wearing a lab coat and seems vaguely horrified to have found himself in the admittedly low-watt glare of the Irish media spotlight.

He is in Dublin with his producing partner and fellow Pixar veteran Jonas Rivera to promote the studio's latest animated venture, Up. Someday Pixar will make a bad film, but Up certainly isn't it. A charming, daring and hugely imaginative animation about an old widower who uses a plethora of helium-filled balloons to fly his rickety house down to South America, it has already done huge business in the US and looks set to enchant cinemagoers here at least as much as Toy Story and Finding Nemo have in the past.

As Docter and Rivera explain to me, it took five years to make and all began with an inauspicious little drawing. "The whole thing came from a scribble on a napkin, basically," says Rivera.

"Pete did this drawing of an old guy hanging on to this bunch of balloons and floating -- we thought it was funny, and we pinned it to the wall in the office. Pete and Bob Peterson [the film's co-writer] had always wanted to do something with an old man character because that seemed to have humour, and then when we started developing it and, while writing the storyboard, we also realised there was room for so much emotion there as well, like thinking about your grandfather, and nostalgia, and history."

"It was the idea of the character that got us started," agrees Docter. "We thought it would be fun to do something with this really grouchy guy, who could get away with slamming the door in people's faces and yet you still like him, like the kind of characters that Ed Asner used to play." Asner, the veteran star of TV comedies such as The Mary Tyler Moore Show and Lou Grant, would ultimately provide the voice of Carl Fredricksen, but Docter and the Up creative team drew on many other influences in creating the animated character.

"We looked at Spencer Tracy in Guess Who's Coming to Dinner and lots of other movies," explains Rivera, "Walter Matthau, Spencer Tracy, James Whitmore from The Shawshank Redemption, they all had a part to play. But we also brought in photos of all our grandparents, and my grandparents lived close, so we'd go to their house and set up a video camera and say, 'hey pop, tell us about that time you got your first truck', and he would just talk ... "

From all of these sources, Docter and his animators perfected a white-haired, grumpy but essentially decent character whose jutting square head represented the boxed-in nature of his life before he and his house take to the skies.

I've always wondered how it is that Pixar have managed to maintain an almost impossibly high standard from film to film, and the answer seems to be an absolutely extraordinary attention to detail. In the five years it took to complete Up, Docter, Rivera and Peterson seem to have left no stone unturned in their quest for veracity and perfection.

Rivera, for instance, remembers an amusing incident early in the project's development. "This guy on the computer science team came in almost in a panic," he recalls, "because he'd done this calculation and figured out that based on the square footage of the house and the year it was built and the raw materials, that it would actually take 23.5 billion or whatever balloons to lift the house, and that we had made a mistake! And I'm, like, 'bless your heart ... '"

To get the film's hilarious talking dogs right, the team studied hundreds of real-life canines, and when designing Up's giant tropical bird they brought in a live ostrich as a model. The film also includes a giant airship, or dirigible. "There's a company in San Francisco who do dirigible tours of the city," says Rivera, "so we got them to fire one up and recorded the sound of the motor for the soundtrack."

In order to make sure that they got their South American backdrops right, Docter and 11 other Pixar artists visited the famously inaccessible Monte Roraima region of Venezuela. And when Rivera saw an old house being lifted onto blocks one morning on the way to work, he called the office straight away. "The whole art department invaded the construction site," he says, "they scaled the fences and climbed under the house and took pictures of all the wiring. They were very excited."

"That's very much the way the Pixar guys go," says Docter, "starting with math and real life, then working backwards from there. I mean, you won't find bigger geeks anywhere in the world. I think I've yet to be there for a full day at Pixar without someone bringing up Star Wars."

"The people there love movies, and whenever we pitch things their approach is, scientifically, what would we need to do to actually make this work in real life, with physics ... " Rivera agrees.

"Pixar is a really cool place," he says, "it's sort of a strange club of computer scientists and animators and movie dorks, but we all have this passion for making these things. We all sort of return to the same question, which is 'why did we go and see Raiders of the Lost Ark ten times when we were kids and how can we get that feeling back?' That's what we try to do."

With Up, as ever, Pixar have succeeded in getting that feeling back, despite the fact that both Docter and Rivera were worried that it might be one of the studio's quieter films. "I guess you never really know box office-wise," says Docter. "We just try to make them as good as we can before we get them out there, but it did feel like maybe it was a little on the esoteric side for most audiences. So it's been a great surprise to have it do as well as it has." Up has already earned almost $300 million on its American run alone.

"I was sitting at the wrap party for WALL-E," Rivera remembers, "I just loved it and was so proud of it, but I remember looking over at Pete and thinking, 'getting anywhere near this is going to be a tall order'. It's not that we're thinking, 'oh, we've got to top WALL-E, in the box office or the reviews', it's just that we're very self-competitive, and it's about being in the same ring as WALL-E, it would have to be worthy of that. I hope Up is."

Rivera has been with Pixar since the mid-1990s, and has seen the company change and grow -- it was formally taken over by Disney in 2006. "It was almost this mom and pop grocery store when I started," he remembers, "where nobody really knew what they were doing. And it's evolved into this massive organisation, with this new building which is like a kind of cathedral to animation. And yet, I can honestly say it has retained that spirit.

"And in terms of Disney's influence, it's actually gotten a little easier since 2006. I mean on Bug's Life, and even up to Monsters Inc, we were showing everything to Disney, every design, and they would give notes, and we'd have screenings down there. But we don't do that any more, it's just us, and we show everything to John [Lasseter], so with producing this film I had it a little easier than the first wave of producers did.

"I actually credit Bob Iger [Disney CEO] a lot -- I remember him coming up to talk to us in 2006 and saying that he'd be making the worst investment in history if he tried to come in and change things, so proceed! And he has stuck to that."

In other words, the Pixar boys have been left to play with their toys, which is good news for the rest of us.

Up opens nationwide on 9 October

- Ed Power

Irish Independent