Not-so-cuddly toy: "Ted"

With Family Guy lumbering into double-digit seasons, rapidly becoming bereft of taboos worth breaking, its creative force Seth MacFarlane has perhaps picked the right time to make the leap to the big screen, taking a good number of his sniggering TV cohorts with him. Ted, which MacFarlane has directed, and scripted with regular FG gagsmiths Alec Sulkin and Wellesley Wild, at first seems to be about putting childish things away and moving on, but though its filthy mind and potty mouth gets it so far as blunt, raucous multiplex entertainment, it doesn't quite have the balls to follow through on its own premise. (As per MacFarlane, all entendres, single and double, are very much intended.)

At the film's centre is a bizarre love triangle, of which the human elements are John and Lori, two thirtysomething Boston residents. Lori (Mila Kunis) is a high-flying PR gal; and, as played by Mark Wahlberg, John is obviously handsome and charming and possessed of seriously great pecs. But the latter is another man-boy, shruggingly content with his low-paying job in car rental, and more concerned with downloading Star Wars ringtones for his phone than in progressing anywhere in life. In this, John has an unusual enabler: Ted, a Ruxpin-like teddy bear who was granted the power of speech, motion and sentient thought at an early stage in his keeper's development, and has lived with him ever since, mostly limited to the couch in John's apartment, and a diet of weed, cheese puffs and regular viewings of the film Flash Gordon.

Ted is recognisable as a familiar MacFarlane line of attack: to take a symbol of innocence, or loyalty, or virtue, and - by assigning it human characteristics - somehow make it dirty, nasty and grubby. His obvious predecessor would be Brian in Family Guy: the faithful pooch who gets superior, even racist - and couch-humpingly horny - after a few Martinis. Again voiced by MacFarlane himself, Ted is very much a character in his own right - a child, a delinquent id, a soul brother - so much so that the movie can, at its midpoint, stage a spectacular homage to the Bourne trilogy's particular brand of on-the-hoof ultra-violence, and you genuinely find yourself fearing for every single pixellated fibre on Ted's virtually furry frame; so much so that the denouement can qualify as suspenseful, even moving, to judge by the gasps and sobs of the audience I saw the film with. Ted has a surer feel for plot and structure than most of its classmates in this particular school of American comedy, which helps. You're reminded of just how far, and how fast, the average episode of Family Guy can travel in twenty minutes - and MacFarlane and co. know all too well how any downtime might be filled with crowdpleasing celebrity cameos and offbeam pop-culture riffs. Here, we get note-perfect Airplane! take-offs and suitably scatty nods to Annie Hall, plus - in what's becoming a bewilderingly crowded field - one of the better Notebook references of recent times.

But there are also problems with the MacFarlane house style. The film isn't averse to the lazy, post-ironic racism, sexism and homophobia upon which Family Guy has become increasingly reliant, and which we're not supposed to mind, so long as we're being zinged every ten seconds. Ted isn't notably generous to Boston's Asian residents, nor its women; where Judd Apatow has traditionally cast strong, sympathetic, funny actresses to compensate for his sometimes underwritten female roles, MacFarlane remains loyal to the pin-uppy Kunis, voice of TV's premier animated punchbag Meg Griffin. Not once is Lori allowed to be funny; one of the reasons John finds it so hard to put Ted down is that life with his furry friend is a non-stop riot of wild parties, wisecracks and impromptu meetings with Sam Jones, where his would-be lovematch is all business talk, expectations of rings, and sulks or pouts whenever John comes home late, or one of Ted's hooker chums takes a dump on the carpet. The film simply isn't mature enough to present its lead character with a viable alternative to his childishness.

As with The Five-Year Engagement's invocation of certain Tom Hanks romcoms, Ted strives to define itself in relation to other movies, contrasting its boysy roughhousing with Lori's love-triangle of choice (Bridget Jones's Diary: god, she really is dull, isn't she?). Yet as manboy dramas go, MacFarlane's film never cuts as deep as Todd Solondz's recent Dark Horse, whose negotiation of separation anxieties proved genuinely awkward and wounding; nor, really, does it dare to go as far as the Australian TV import Wilfred, which dragged a similar set-up (bachelor boy led astray by furry best friend) into 18-rated territory. It may be telling that, rather than resolving the it's-me-or-the-bear quandary, the ending settles for a compromise designed to assuage those gurgling folks in the audience who actually like Ted, and will no doubt get to hang out with him some more in several direct-to-DVD sequels. Hey, MacFarlane seems to be saying here, let's not put childish things away too soon.

That the movies have co-opted MacFarlane's talents now, at a moment when the edge is beginning to come off his blade, may be understood as yet another sign of just how far behind television the American mainstream has started to lag. One of Family Guy's implied aims, when it first arrived on TV in 1999, was to explode the hoarily traditional sitcom format, or at least subject it to death by a thousand cutaways. (In this, it was hardly revolutionary: Roseanne had got there a decade before, although with a lower level of snark.) That goal achieved - can anyone now look at Everybody Loves Raymond re-runs without a strong sense of being back in another century? - television has reclaimed the body and done something unexpected with it, as evidenced by Weeds, Arrested Development and Modern Family, all of which owe something to the Family Guy model. One of MacFarlane's own side-projects has been The Cleveland Show, a FG spin-off that lampoons those 1970s/80s black-oriented sitcoms like The Jeffersons with a far mellower, more affectionate tone than its abrasive progenitor; mellow enough, at least, that it's all the more surprising when a truly radical or subversive line or idea pops up. Ted is too frantic - too desperate to impress MacFarlane's new bosses, too keen to tickle or piss off an audience - to arrive at that winning mellowness: it has a furry pawful of good, honest laughs, and it'll do for a Saturday night, but it's Cleveland who continues to generate the biggest chuckles in the MacFarlane armoury. Television wins again.

Ted is in cinemas nationwide.