The line between adult and children's entertainment has blurred in recent years - just look at movies like Babe, Shrek, Finding Nemo, and Harry Potter to see the evidence. Add to that list The Triplets of Belleville, although this wildly imaginative animated feature from Montreal-based director Sylvain Chomet and crew, is in a class of its own.

A black comedy, that is as unsettling as it is touching, it combines vivid characterisation with edgy humour and grotesque imagery. There is no dialogue or narration - characters more like grunt, mumble, snort, growl or squeak - and the swinging soundtrack riffs nostalgically on numbers from the musical hall and jazz age.

The story begins with a sad, little boy, Champion, who lives in an old towered building among the rolling hills of the French countryside. Each day, he sits on the edge of his bed, head hung in a state of lonely tristesse while the mellifluos tick-tock of a grandfather clock marks time.

His grandmother, Madame Souza, a bespectacled, little old lady with a club foot, tries to lift his spirits with presents. But he always ends up slumping back into his depression, even when given an enthusiastic puppy called Bruno. Then she gives him a tricycle. He takes to it in a flurry of joy, and it becomes his friend for life.

Moving ahead in time, we meet Champion as Tour de France contender. The faraway look of calm in his eyes and his grotesquely musclar legs reveal how he has grown at one with his machine. Granny Souza has turned training instructor, a job that involves pursuing him through the streets, rhythmically peeping a whistle that is welded to her lips, and massaging his back at night with a lawn mower.

Success beckons, but in the Tour itself, while climbing through the Alps, Champion is kidnapped by two sinister triangular-shaped men in black. As the captors set sail across the ocean in a liner the size of a skyscraper, Mme Souza and Bruno, give dogged pursuit in a pedalo. The journey takes them to Belle Ville (a caricature New York), where she meets the Triplets. This eccentric elderly threesome, who skiffle on household implements and sing harmonies in the style of the Andrew sisters, help Souza save Champion from the French mafia.

Bizarre is rarely so enjoyable. Where else will you find Fred Astaire eaten by his tap-dancing shoes? Or an instrumental solo played on a vacuum cleaner?

The animation style, which uses a mixture of handrawn and digital techniques, has a very fluid and richly textured quality. The detail of the city and land-scapes is wonderful. The visuals move from crazy swirls to a point where on the ocean-crossing, the colours have so much depth it is like watching a gigantic oil painting in motion.

The characterisation is particularly memorable because it is so stylised: the Tour de France cyclists who are depicted like thoroughbred horses, the obese Belle-Villians, the triplets who survive on a diet of frogs, or the obsequious maitre d' who bends over so far backwards that he is looking at the world upside-down.

So much much invention deserves more than one viewing.