Jimmy, the boy genius, makes shrink rays out of the t.v. remote and launches satellites made from toasters into the stratosphere in his idle time before catching the school bus. His parents, loving but slow-witted variations on the Cleavers, don’t seem to appreciate their little prodigy, and to the kids at school he’s just another nerd. Until, of course, space aliens abduct Retroville’s parental units and Jimmy has to turn the local amusement park rides into nuclear-powered interplanetary assault craft.

The aliens are basically sentient, sinister balls of snot sloshing about in floating eggs (voiced by Martin Short and Star Trek’s Patrick Stewart), and the parents are to be sacrificed to their godzilla-like poultry god, but only after they’ve been made to do the chicken dance for a packed stadium of snot-eggs. That’s pretty much as much plot as the movie can stand. Like most of the computer-animated marvels that seem to reach the market these days, it’s not the story that counts but the implausible experience that can be generated free from the restraints of camera, film, and actors.

Jimmy Neutron’s animation style is an extension of the Toy Story universe, a vision made of jet-moulded plastic, all slick, rounded surfaces and elastic skeletons in candy colours. The camera work is just as garish, eager to send us on rollercoaster joyrides whenever the action seems to flag. Which is rare -- like an eager puppy, the film ricochets all over the place, encouraging parents to note the detritus of their own cultural childhood in Retroville’s cluttered landscape while taking the kids on yet another vertigo-inducing ride. It’s junk-food moviemaking, pleasantly free from aftertaste or originality.