Whenever I hear a film hailed as ?an instant classic?, I start to grow suspicious. This suspicion increases when I hear it is ?a sleeper hit?, swells when I hear it is ?heart-warming?, and positively balloons if I hear the phrase, ?it made me laugh and cry?. So it was with a very suspicious mind that I prepared to see Knocked Up, the romantic comedy that has taken America by storm.

Within approximately three minutes, all my suspicions were laid to rest. Saying Knocked Up is likeable is like saying Lindsay Lohan can be a bit of a handful sometimes. This film is the ultimate charmer, combining intelligent commentary on twenty-first century relationships, emotional truth, post-modern scriptwriting and more dick jokes than you can shake a phallic stick at. While this may not exactly be fun for all the family, it is certainly a film with enormously wide-ranging appeal, with enough wit and originality to satisfy even the most cynical of moviegoer.

The concept is simple enough: lovely blonde E! channel presenter Alison (Grey?s Anatomy?s Katherine Heigl) beds goofy stoner Ben (Seth Rogan) on a drunken celebratory night out. Two months (and twenty pregnancy tests) later, Alison discovers she has a mini-goofy stoner on the way, and tries to make a go of things with Ben.

The unbelievably stunning girl/wisecracking geek pairing is certainly nothing groundbreaking (evidently some serious wish fulfilment going on around Hollywood writing tables), but what is impressive is writer/director Judd Apatow?s ability to bring both shockingly off-the-wall humour and realism to this fairytale scenario.

Katherine is not the tiresome straight man to Ben?s loveable jokester, but a sympathetic, three-dimensional human being, genuinely scared and confused by her predicament, and in equal parts exasperated and comforted by the sweet but hopeless Ben. His refusal to take their situation seriously is part of his boyish charm, but is also a damaging character flaw. Apatow revels in Ben?s pop culture knowledge and Jewish underdog humour, but also demonstrates that he is unfit to be the partner that Katherine needs him to be.

However, Knocked Up is not shaped around the usual romcom magical transformation; although Ben does make some effort to adjust to the role that has been foisted upon him, he is not about to make tracks for the nearest merchant bank or real estate firm, continuing to focus on his website ?fleshofthestars.com?, recording movie scenes in which famous actresses appear naked.

Apatow clearly shows the negative consequences of Ben?s emotional immaturity, but does not encourage his audience to simply condemn him for his juvenile lifestyle and inability to accept a traditional social role. Ben?s loutish housemates may not be financially successful, or even particularly hygienic, but they are at least happy, a state that Katherine?s uptight suburban sister and her husband struggle to obtain.

It is in the creation of desperate housewife Debbie (Leslie Mann) and downtrodden husband Peter (Paul Rudd) that Apatow really triumphs, providing us with a painfully realistic portrayal of domestic bliss turning to domestic misery. Debbie is brittle, judgmental and insecure, yet never a cold-hearted villain, and her frantic attempts to retain her good looks and youth in order to convince Peter to spend time with her give the film some of its funniest and most moving moments.

Peter, meanwhile, is a cautionary tale for Ben, the little boy who did grow up and discovered that being a grown-up sucks. His morose teenage backchat and mutinous attempts to escape the shackles of family life are, like Ben?s antics, both hysterical to watch and visibly hurtful to the woman in his life.

In addition to the central foursome, Apatow provides his audience with an abundance of unique and hilarious supporting characters, including an incessantly bitchy TV producer, a brutally honest editor, a straight-talking bouncer, and a stream of eccentric gynecologists. The humour shifts subtly throughout the film, from dark, emotional jokes to witty one-liners, and from surreal and cerebral to downright dirty.

For one particularly shocking gag at the climax of the film (dubbed ?the final frontier?), Apatow noted in his script, ?You will see everything. This is not The Cosby Show.? In Knocked Up, you will indeed see everything ? heartbreak, humour, love, sex etc. ? and I guarantee it will make you laugh, and it will make you cry.