As Sin City proved, there's nothing so outlandish that it can't now be realised on screen using state-of-the-art digital technology. But just because it can be done doesn't mean it should be. And the proof of that sticky pudding lies in Robert Rodriguez's latest, a frenetic, nonsensical and often frustrating mess that shows just what can happen when a filmmaker puts pixels before plot.
Rodriguez's insistence on giving Frank Miller a co-helmer credit on Sin City led to him resigning from the Directors Guild. But it's the Writers Guild who'll be pissed at Sharkboy, based as it is on characters and concepts dreamed up by his seven-year-old son, Racer Max. Not that there's anything wrong with keeping things in the family; after all, it's part and parcel of Rodriguez's status as a DIY auteur. But on this evidence, his passion to make his kids' reveries a reality has entirely robbed him of objectivity: for every good idea here there's a couple of very dodgy ones.
The worst of the lot is the belief that the multi-coloured landscapes of the admittedly imaginative Planet Drool will look even more vivid from behind 3-D glasses. (Punters are told to don cardboard spectacles whenever the action leaves the real world.) Unfortunately the reverse is true, the primitive red-and-green filters reducing everything to a muddy, indistinct brown.
Spy Kids 3-D had a similar problem, although there were compensations - not least Sylvester Stallone hamming it up in multiple roles. No such luck with Sharkboy, which puts its faith in precocious unknowns with little of Sly's charisma. Latino stand-up George Lopez has a gas as the nefarious Mr Electric, a giant walking alarm-clock with bolts of lightning where his limbs should be. But he's the only bright spark in a chaotic caper designed to get kids bouncing off the walls while adults nurse migraines.
The Rodriguez juggernaut stutters to a halt with a misguided fantasy that has little of the playful charm and sly wit of his Spy Kids movies.