Ali G Indahouse (15)

We is gettin' a bit overexposed

The Ali G Paradox, as it's known, goes like this: the character was devised as a loser, a white, home-counties thicko who lives with his nan, but who talks and dresses as if he were an Uzi-toting gangsta from south central LA. And yet this character, along with his creator, Sacha Baron Cohen, has risen from being a spoof interviewer on the 11 O'Clock Show in 1998, to having his own series, turning up in a Madonna video, presenting the MTV Europe Awards and releasing a single with Shaggy - none of which has anything to do with being a sad wannabe from Surrey. With every extra mile that Ali G ascends, the concept of the character is left further behind.

The feature film is the latest example of this paradox. Ali G Indahouse starts hilariously by refining the initial wannabe idea and showing us what life is like on the mean streets of Staines. We see that Ali's gang, the West Staines Massive, has a total of three members (Ali's sidekick is the excellent Martin Freeman, aka Tim from The Office). And we witness a road race with the East Staines Massive: everyone is careful to keep to the 30mph speed limit.

Alas, the rules of the Small Screen To Big Screen Transfer being what they are, Ali can't stay in his 'hood for long. Kevin and Perry went to Ibiza, Mr Bean went to California, and Ali G goes to Westminster. Charles Dance's scheming Chancellor of the Exchequer drafts him into the party in order to disgrace the Prime Minister (Michael Gambon), but, wouldn't you just know it, Ali has a shock victory. And once he's Indahouse of Commons, he implements his key proposals: free cannabis on the NHS, asylum seekers to be admitted only if they're "fit" women. These scenes are funny enough until you compare them with Ali G's first appearances, back when his interviewees didn't realise there was a Cambridge graduate beneath the Hilfiger shellsuit. He used to suggest outrageous policies to spluttering MPs; now he suggests outrageous policies to actors pretending to be spluttering MPs, which isn't the same thing.

What we're left with isn't much more than a bunch of rude jokes gaffer-taped together. But so what? That approach didn't do Wayne's World and Austin Powers any harm, and Cohen is at least as charming a performer as Mike Myers is. Basically – and basic is the word – Ali G Indahouse fulfils the only criteria it wants to. The gags may be the worst and the crudest you've heard since you were in the playground at primary school, but you'll laugh at them as much as you did back then. He hasn't stopped ascending yet.

The Experiment (18) is a German dramatisation of The Stanford Prison Experiment, an infamous role-playing exercise conducted by an American university psychology department in 1971. A group of volunteers was divided into "guards" and "prisoners" and instructed to stay in character for several days in a mock-up jail. With terrifying speed, method acting took over. The warders became tyrannical, the "prisoners" as inured to mistreatment as if they were bang-to-rights convicts. It's fertile ground for a film – so much so that almost any deviation from the true story can only detract from it.

Oliver Hirschbiegel, The Experiment's director, deviates from the true story. He adds a hero, Tarek (Moritz Bleibtreu), a man with an insubordinate streak right out of One Flew Over The Cuckoo's Nest, and a girlfriend whose off-campus scenes only dissipate the claustrophobic tension. Hirschbiegel also strays from the facts by letting the situation escalate to a generic action-movie finale of chases and shoot-outs. Happy to acknowledge the influence of David Fincher (Fight Club), he's taken an American story, moved it to Germany and ended up being too American.

That said, The Experiment has got all the youthful energy and edgy style of the thrillers Hirschbiegel admires. He is a sly observer – he captures the guards' testosterone buzz as they eye up their truncheons and handcuffs – and there is a philosophical substance that outweighs most thrillers as slick as this. For all the warders' jurisdiction and Tarek's insurrection, they're all prisoners, conforming to the roles they've been handed.

The Officers' Ward (15) is another European chamber drama that's based on actual events. Caught in a shell blast at the very start of hostilities, Lieutenant Fournier (Eric Caravaca) sees out the First World War in the military hospital ward of the title. He needs five years of plastic surgery to piece together his obliterated face, so for him the War is over almost before it's started.

The issues are engrossing. Francois Dupeyron's film is a war story with only a glimpse of the battlefield; a story whose hero – and his visitors keep telling him that that's what he is – did nothing courageous except enlisting. My only cavil is that these ironies are implied rather than explored. Perhaps too wary of being sentimental, the film grants Fournier very little emotion, and we'd be more moved by his recovery if he weren't such a cipher. If The Experiment could have done with a touch less Hollywood, The Officers' Ward could have done with a touch more.Still, this is a dignified, tender study of friendship, family and convalescence – inner and outer.

Now for some cartoons. There are three out this week, including Return To Never Land (U), Disney's middling sequel to its Peter Pan cartoon. It adds nothing to the original except some glutinous Lilith Fair balladeering. The other two cartoons are computer generated, so you can't help measuring them against Shrek and Monsters Inc. Indeed, Jimmy Neutron: Boy Genius (U) is competing with both of those films for the animation Oscar, but neither it nor Ice Age (U) comes near them for extravagant detail in its script or visuals.

They're fun, though. Technology aside, Ice Age is the sort of cartoon Disney was making before they started being knowing and self-referential. It's an adventure in which a mammoth, a sloth and a saber-toothed tiger find a human baby and overcome all sorts of perils to restore it to its tribe. The best bits are interludes featuring a frazzled prehistoric squirrel who's trying to bury an acorn in the permafrost. They're as blissful as anything animated by Chuck Jones or performed by Harold Lloyd. Aimed at a younger audience, Jimmy Neutron sees a pre-teen, nuclear age Heath Robinson rescuing his parents from slimy aliens.

Ikingut (nc) is a good-hearted, simple children's film set in an Icelandic village a few hundred years ago. When an Inuit boy arrives, the superstitious locals assume he's a demon and/or a flying polar bear. Ali Zaoua (15) is a crushing exposé of life among the broken-toothed, glue-sniffing young boys on the streets of Morocco. Its actors are real street children.

n.barber@independent.co.uk

Jonathan Romney is away