Youth in Revolt, Miguel Arteta, 90 mins (15)<br/>Astro Boy, David Bowers, 94 mins (PG)

Michael Cera has to be one of the most unlikely movie stars since Fatty Arbuckle.

He made his name in the wondrous if short-lived cult sitcom Arrested Development, but considering that he played a gangly, hesitant, virginal teenager, you wouldn't have picked him out as the break-out leading man from that series. Since then, though, Cera has played a version of that very character in Juno, Superbad, Year One, Nick and Norah's Infinite Playlist, and now in his first starring vehicle, Youth in Revolt.

This time the character is named Nick Twisp, a suburban 16-year-old whose father (Steve Buscemi) has run off with a 20-year-old Barbie doll, and whose mother lives with whichever unsuitable boyfriend comes her way. Nick, a lover of vinyl albums and foreign films, fears that he's doomed to loneliness until he meets a girl called Sheeni (Portia Doubleday) who's even more verbose and precocious than he is. But Sheeni already has a tall, blond boyfriend who's a champion windsurfer and writer of "futurist percussive" poetry, so Nick dreams up a cocksure alter ego, also played by Cera, who materialises every now and then to spur him on, like Humphrey Bogart in Play It Again, Sam. Youth in Revolt is basically Cera's comedy persona distilled into a film. It's sweet, likeable and tinged with mel-ancholy, but it's also unashamedly nerdy and wordy, with a far higher IQ than the average teen comedy, and a winning way of presenting the most absurd events with casual naturalism. You could see it as a less smug, less annoying Juno.

But if Juno tilted gradually from contrivance to unironic emotion, Youth in Revolt tumbles in the opposite direction, away from the sparkling interplay between Nick and Sheeni and towards so much random daftness that Nick ends up as a cross-dressing arsonist on the run from the police.

It's no surprise to learn that Youth in Revolt is based on a picaresque 500-page novel: it tries to cram in so much of its source material that it's bursting at the seams. As for Cera, his delivery is impeccable, but if he does not extend his range soon, "arrested development" is going to stand as a career summary.

Osamu Tezuka's Astro Boy was hugely influential as a comic strip and then a TV series in Japan in the Fifties and Sixties. Astro's new computer-animated outing won't have quite such an impact, but it's still a fast, fun superhero adventure, with everything you might want from the tale of a robotic youngster who zooms through the skies above a floating future city.

Beware, though – the opening scenes leave a sour taste that the rest of the film can't quite wash away. First, a lovable lad named Toby is obliterated by a weapon built by his own father (voiced by Nicolas Cage). Next, the bereaved dad constructs an android duplicate of Toby which thinks it's human. And then, when it discovers it's a robot, its creator declares that it could never replace his son, anyway, and that he never wants to see it again. Ouch. Parents of young cartoon fans might prefer to rent the DVD, and skip past the first half hour.

Next Week:

Nicholas Barber sinks his teeth into The Wolfman, starring Benicio Del Toro, Anthony Hopkins and Emily Blunt, and finds out whether its long-postponed release is a bad sign

Also Showing: 07/02/2010

The Island (112 mins)

Featuring considerably fewer exploding helicopters than the Michael Bay movie of the same name, this eccentric yet grave Russian drama is set around a monastery on a snow-covered island where the wizened boilerman is reputed to be a healer and a prophet. It may appeal to those who fret a lot about their immortal soul.

Tony (78 mins, 18)

Unlike most cinematic serial killers, Tony isn't a flamboyant mastermind, but a moustachioed dweeb who traipses London's grubbiest parts murdering strangers. Promising, but more a character sketch than a fleshed-out film.

Holy Water (93 mins, 15)

Four Irishmen hijack a van of Viagra in this incompetent would-be Ealing comedy. The Irish should boycott it for portraying them as brainless yokels. Everyone else should boycott it just because it's dreadful.