Depend on humans to mess up a good thing.

Wall-E, with Ratatouille, The Incredibles and Toy Story, is that rare thing – a children’s film that transcends its category. Its opening third, mostly without dialogue, is a stunning achievement, a lyrical, magical evocation of an imaginary space that feels absolutely true to itself. In fact, the only time that Wall-E falters is when it tries too hard to be a children’s film, with cuddly humanoid characters, fast-moving plot and too-pat resolution. The final two-thirds of Wall-E are not bad at all…just a step down into popcorn fodder from an opening that felt like art.

Wall-E is about loneliness and connection, a deeply human conundrum acted out, paradoxically, by non-human characters. It opens with the chilling perfection of star-filled space, a plaintive verse of “Out There” from Hello Dolly underscoring this world’s essential melancholy. From this vantage, the camera begins hurtling towards Earth, crashing through a junky layer of abandoned satellites to ponder smoggy mountains of trash. The garbage has been compacted into squares and stacked in giant piles that tower above deserted skyscrapers. It’s a dead landscape, viewed through a smoky haze, until you notice something small squeaking in the bottom corner of the screen. Moviegoers meet Wall-E, robot, trash compacter, lover, dreamer and physical comedian par excellence.

The opening scenes, in which Wall-E frolics among the ruins of civilization — working, certainly, but also finding time to play delightfully with a padded bra, a paddle ball, a diamond ring in a box (he keeps the box) — are a miracle of light-handed grace. Wall-E communicates his curious, humorous moods through the most delicate of gestures, a squinch in his binocular eyes, a hunch in his snake-metal neck, a buzz or whir or beep. He squeezes garbage into boxes like a child making mud patties, with evident pride in his efforts, but he also takes time to appreciate the odd bits he finds. One of these odd bits turns out to be a green seedling, the only one on the planet, and the key to whole plot of the movie.

Wall-E, a mechanical Charlie Chaplin, is the heart and soul of the movie that bears his name. His co-star Eva, the sleek robotic life probe on the hunt for exactly the kind of greeneage Wall-E has found, is also rather good. You can read a whole palette of emotions in the shifting shape of her electronically generated eyes – and a range of thoughts in her squeaks and distorted buzzes. The two of them meet cute, old movie style, if you can define meeting cute as the boy almost getting fried by the rocket jets of a landing spaceship. They are opposites of a type that have always attracted in the movies, Eva aerodynamically streamlined like an iPod, Wall-E battered and filthy as a Tonka truck left out over the winter. You could even see Wall-E as another one of those movies in which a career-oriented, successful female gets waylaid by a loser boyfriend (calling Seth Rogen), except that it is Wall-E who does Eva’s job finally, finding the plant and putting it where it belongs.

These opening scenes, where we enter Wall-E’s world, meet Eva and see the two of them form a connection are remarkably powerful, but they are not the typical elements of a plot-driven movie. Later, as things begin to happen – Eva goes into a coma, a space ship arrives to take her away and Wall-E clings to it to rescue his love – the magical part of this film recedes. There are still some extraordinary moments in the later half of the film – one where Wall-E and Eva fly together outside the space ship – but we have mostly descended into cartoon world good guys and bad guys. It becomes a popcorn movie, maybe a good one, but not as great as it started out to be.

One of the problems is that the humans in the second half are not very interesting. As a plot point, they have grown soft over centuries on the Axiom spaceship, losing bone density as they ride their hover chairs everywhere, losing human contact as they communicate with one another through computer screens. They are vast, doughy blobs, bored with themselves and their easy life. Even the ship’s captain seems remarkably complacent and dull – though his rebellion is meant to give us some hope that the human race can eventually recover.

Yet the plot, too, turns flabby and predictable. There are misfit robots to be rallied, bad guys to evade, quirky friendships to be struck and Screenwriting 101 character growth arcs to be followed. Wall-E turns into a conventional movie in its second half, entertaining and astonishingly technically accomplished, but vaguely disappointing.

Extensive bonus materials hint at both halves of the equation, explaining exactly why the first half was so great and why the second half faltered. A short documentary called “The Imperfect Lens” explores the lighting and camera work innovations that made an imaginary world seem so visually resonant. The director, we find, went so far as to bring in live action cinematographer Roger Deakins to consult about how lighting and camera lenses work in the real world. So when Eva is transfixed by the flame of a Bic lighter in Wall-E’s junk-filled home, the light from it looks as soft and golden as it might in real life. When she accidentally powers up an electric bulb, the light is sharp and golden.

The film, though created entirely on computer, replicates the way that a live action film might look, right down to the way the cameras focus. A shot of Wall-E crashing a few dozen grocery carts zeros in on him, crystal clear in the background. Eva, in the foreground, is slightly blurred, as if she had walked, accidentally into the shot. Deakins seems slightly bemused by his role in the film. “There are these artifacts that lens manufacturers in Germany have been trying to eliminate for decades,” he says. “It seems kind of weird to be trying to replicate them here.”

The film’s sound is also an integral part of this imaginary universe, and in “Building a World from Ground Up” we get a sense of exactly how much effort went into the element of the project. The film focuses on Ben Burtt, who is credited with Wall-E’s voice. Ben who? We learn that even if Burtt is not be well-known as an actor, but he is an academy award winner in sound design and the architect of Wall-E’s auditory overlay. We also get a sense of how Pixar’s team has begun to mine the resources of its Disney parent for this film. Burtt prowls through the Disney sound labs, unearthing old equipment and, for its time, very innovative sound technology. He demonstrates Disney’s SonaBox, a 1940s precursor to the vocorder, as well as rain and wind machines. Intercut, we see footage of legendary sound designer Jimmy McDonald, who created many of these machines for Disney’s animated films.

These two short films go a long way towards explaining exactly how real Wall-E’s world was made to seem, through lighting, camera angle and focus and sound. A third piece, called “The Captains Log” gives some insight into how the weaker final sections were developed.

Interestingly, the first act of Wall-E was developed first – and seems to have consumed the largest share of the director and crew’s attention. Yet, in order for the film to work as a story, Eva had to be taken away and Wall-E had to rescue her. The abductors, at first, were intended to be aliens. Animators created green gelatinous creatures that jiggled and bounced in motion. These creatures didn’t even speak intelligible English, but rather a series of grunts and squawks. The animators got quite a ways along with this concept before the director began to test it. The aliens stopped the story dead, and people didn’t like them. The artists went back, literally, to the drawing boards, and began to develop human characters.

Yet while the movie’s human characters may be an improvement over walking, talking green jell-o, they are not anywhere near as fully developed as the robots. In a deleted scenes section, Stanton explains how important it was to have Wall-E in a critical scene where the Captain learned about the mission to recolonize Earth. Without him in the picture, even half hidden under a computer console, the story falters. There is no Wall-E without Wall-E.

Yet you cannot help thinking that there could well have been a Wall-E without human characters, with Wall-E and Eva navigating their mysterious world alone and together. It might not have been a children’s movie. It might not have generated the fast food tie-ins and toy deals of the finished piece. Still, I would like to have seen that movie, even if this one, with all its faults, is still very fine.

RATING 8 / 10