In Pixar’s magical animation, WALL-E, the last human being to leave the planet forgot to switch off the lights. Why bother? Earth is a pigsty, a toxic wasteland of pure rubbish. The only “living” things left are a cockroach and a talking garbage disposal unit that trundles around skyscrapers of junk collecting ancient knickknacks (bubble-wrap, a Rubik’s cube) to store in his metal container home. The dented robot has binocular eyes, metal arms and a pair of ropey caterpillar tracks. Seven hundred years spent compacting rubbish into neat cubes and watching a scratchy video of Hello, Dolly! have done weird things to WALL-E’s circuits. He aches with loneliness. He longs to hold a female claw in his own.

The first half hour of Andrew Stanton’s film is Pixar’s most original bit of thinking since Toy Story. WALL-E (short for Waste Allocation Load Lifter Earth-Class) is not the first tin can with emotions. Science fiction is littered with lovesick robots. But it’s the retro art that captures the imagination. The future unspools like an old-fashioned silent movie. Barely a word is spoken, yet the sepia images reveal a dystopian marvel.

Having trashed the planet, the human race has simply decamped to a massive five-star intergalactic hotel. Seven centuries of spectacularly large lunches in the Milky Way have left human astronauts too fat to walk even if they could remember what feet were for. Armies of ultra-smart robots coddle and scrub these obese babies on their floating beds.

Back on Earth, the epic silence is broken by a shiny probe with beautiful blue eye sockets. Her name is Eve (Extra-terrestrial Vegetation Evaluator), and her green mission is to find proof of organic life. A single tiny plant will trigger the return of human beings. The U-certificate theory is that blubbery humans can become grateful farmers again.

WALL-E is too smitten to care. He moons around Eve like a rusty Woody Allen. She is several generations younger than he is, and not terribly au fait with Hello, Dolly! But WALL-E proves to be as determined as the lunar and loony slot machine Wallace and Gromit encountered in A Grand Day Out. He treats Eve like a matinee idol, and courts her with his rusty gadgets. It’s these Heath Robinson scenes that make the romance such a touching watch.

But the clever whimsy begins to sour the moment the film scrambles on board the Axiom (the pompous name of the human space ark). Our metal heroes fall foul of a rogue computer with delusions of grandeur, and the story turns into a rather predictable robots-in-peril adventure. The film never recovers its anger and eerie poise. The Keystone Kops chase scenes on the spaceship fall short of the nightmare invention of Monsters Inc. And the ending is frankly barmy. But these are forgiveable sins for a film with such great visual reach and huge family appeal. For once, the artful nods to Huxley, Kubrick and Philip K. Dick are not the preserve of trainspotters.

U, 103 minutes

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