Technically dumbfounding, consistently hilarious and genuinely moving - Pixar's latest feature Wall-E raises the bar for animated movies to new heights. "What keeps us going is the desire to stick our necks out. To do anything else would be boring," it's director Andrew Stanton tells Donald Clarke

IT MUST be nice to be a Pixar director.

Every few years, you are put in a plane and taken on a tour of the world's swankiest hotels. Various media wastrels then shuffle before you and, one by one, ask you to explain how you got to be the world's greatest genius. Now, Dr Sycophancy is no stranger to the entertainment industry, but the vociferous praise directed at Pixar is generally sincere and justified. From Toy Story in 1995, through to Finding Nemo in 2003 and Ratatouille in 2007, the animation studio has established a formidable reputation for combining beautiful stories with even more beautiful digital images.

Some bitter little part of my psyche almost hopes that Wall-E, Pixar's latest feature, will finally see the folks from Emeryville, California, laying a big rotten egg. Nobody deserves this level of success. But it is not to be. The film, which follows the last robot on Earth as, over several centuries, he cleans up the detritus left by humanity, is technically dumbfounding, consistently hilarious and genuinely moving. It is, in fact, a serious contender for the best animated feature ever.

Andrew Stanton, the film's director, sits on a couch awaiting adulation. I wonder if he and his colleagues ever get blase about the praise. "Oh, goodness no," he says with a convincing gape of horror. "If anything, we work harder on these films now than we did at the beginning. What keeps us going is the desire to stick our necks out. To do anything else would be boring."

Most of the top people from Pixar, though overpoweringly smart and consistently chatty, dotend to look a little as if they have emerged from mom's basement. John Lasseter, who founded the company and directed the Toy Story movies, insists on wearing "funny" Hawaiian shirts to press interviews. Pete Docter, director of Monsters Inc, looks like a combination of Goofy and Peter Crouch.

By way of contrast, Andrew Stanton, who also gave us the gorgeous Finding Nemo, is a surprisingly presentable fellow. Dressed in a crisp sports jacket and pressed slacks, he could easily be mistaken for a holidaying dentist or a successful small businessman. A graduate of the prestigious California Institute of the Arts, Stanton has been a part of the Pixar story from early on.

Lasseter, a fan of Andrew's early shorts, hired him as the company's fifth employee. The studio always identifies itself as "director-driven", but all the major players in the operation - including chief executive Steve Jobs, co-founder of Apple Computers - do still have an input into every production.

An early teaser trailer for Wall-E explained how the character was devised in the mid-1990s at a lunch attended by Lasseter, Docter and Stanton. Eager to find a successful follow-up to Toy Story, the team toyed with the idea of a film focused on "the last robot on Earth", but eventually decided to develop the project that became A Bug's Life.

"There were hundreds of lunches, but that wasmemorable because two fully formed ideas came out of it: A Bug's Life and Wall-E," he says. "I was intrigued by the idea of doing a science fiction movie featuring a machine that couldn't speak as we speak, but could only talk like a machine. But I don't think we were good enough storytellers at that stage to make that work."

Docter tinkered with the notion for a few months, before eventually casting it aside to work on Monsters Inc. "Then, after I was finished with Nemo, I knew it had been thrown in this box, as it were. So I asked if I could have a crack at it." Stanton describes the original concept of Wall-E as "arty" and, though nobody would confuse the final product with the work of Tarkovsky, the team at Pixar have, indeed, taken risks with the audience's patience.

The opening 40 minutes follow Wall-E - a rusty metal box with ET's eyes - as he potters charmingly about an Earth engulfed in filth and waste. Human beings, eventually overcome by pollution and overcrowding, have left the planet for a life in outer space.

Pixar personnel always get a little sensitive when you remind them that a significant portion of their audience is made up of children. But the folk at Disney, the studio's corporate partners, must have shuffled collectively in their seats when they heard that the first half of the film would be largely without dialogue.

"I wouldn't say that," he says. "But even if they had, then that would be their problem. If they decided to not give us money tomorrow, then that's fine. We'd carry on without them. That's what's great about working with Steve Jobs. He doesn't want anybody to have to settle for second-best."

Still, some critics, desperate to find something to whine about, have noted that recent Pixar films do, perhaps, include a lot of material that might bemuse younger children. Remember all that chatter about probate and the role of the critic in Ratatouille? What about the long wordless sections of Wall-E? Stanton bristles.

"We have never accepted that our core audience is children," he says. "We have never accepted that our films have a role as babysitters. We have always been consistent about that. I loved the great Disney films when I was nine. I loved them when I was 29 and I love them now. We make the films that we want to see and, if that makes us immature, well then so be it."

So he doesn't see the long quasi-silent sequence as a risky move? "It's funny. If you talk about it, you can trick yourself into thinking it is risky. But for 30 years in the last century, nobody thought silent cinema was risky. Everybody - people of all ages - accepted it. Every day, while making this film, we would watch a Chaplin film or a Keaton film and we realised something about the equation that makes comedy work.

The audience finds it funnier if they can work out that two plus two equals four themselves. Solving the puzzle for yourself makes the joke funnier." I suspect that Stanton and his colleagues are perfectly sincere when they say they don't ponder demographics when planning their films. But his responses to questions about the film's apparent ecological message are more puzzling.

Wall-E's "life" (is that the word?) is eventually disturbed when Eve, a milky white, apparently feminine probe - a kind of iPod with blasters - arrives to search for any remaining life on Earth. After many mishaps, Wall-E and Eve end up on the massive spaceship that contains the remains of our species. It transpires that humans, after destroying the planet by filling it with garbage, have gone on to evolve into enormously fat, mentally passive blimps.

If ever there were a film with an evolutionary message, it is Wall-E: keep going the way we are going and we'll bugger up the planet. So why has Stanton hitherto denied that any such message exists. "Because it doesn't," he says. Yes it does! I know he spent six years making the film and that I'm just some schlub in the third row.

But, even if he didn't intend the film to have a message, it still speaks to current concerns about the planet's malaise. "I suppose that is what I amsaying. I'm saying I didn't intend it. If you watch the film, you see we were just using plant life as a symbol of hope. Basically, I needed some way of making Wall-E isolated and to get everybody else off the Earth. Trash is very visible.

It works on screen, so that's why I used it. Everybody knows about buying too much stuff, so that works as an image. It just worked for the story. Simple as that. Now, I find people are accusing me of . . . " But, hang on a moment. It's not an accusation. Why does he feel the need to distance himself so completely from suggestions that the picture might be waving the green flag?

That would be a good thing. Wouldn't it? "Okay. I can look myself in the mirror and say: if people are using the film in that way then it's not a bad message to be associated with. But I would be lying to you if I said that's why I put it in."

A quick glance at responses to Wall-E in the US offers clues as to the source of Stanton's caution. On the left, bloggers for the Huffington Post have complained that the film doesn't offer enough ecological advice to consumers.

On the right, fulminators for the National Review denounce the picture as "leftist propaganda". Who would blame Stanton for retreating to his ideologically neutral basement and erecting the storm windows? Nobody wants to be caught in the crossfire from these culture wars.

To be fair, like all Pixar's best films, Wall-E, despite its concern with robots, spaceships and the end of the world, works best as a touchingly humane drama. Stanton, who has been in the same relationship for 25 years and has two teenage children, agrees that little personal crises inspire their stories.

"I remember walking with my son when he was little and I realised that I had trouble just connecting with him because I was so concerned about the dangers facing him. 'Don't go there! Careful of the road!' And that became the basis for Finding Nemo." Is that the key to Pixar's success? Do they succeed by injecting the fantastic into the everyday? "Maybe. But, you know, it's a shame that everyone's not doing that. All stories should begin with the personal."

• Wall-E opens nationwide today