Judd Apatow deserves plenty of credit for his contributions to comedy – among them, TV’s late, lamented Freaks and Geeks, The 40-Year-Old Virgin and the discovery of Seth Rogen – but one of his masterstrokes has been overlooked until now: the pairing of Paul Rudd and former Freak Jason Segel.

Though Apatow’s name appears nowhere in the credits of I Love You, Man, his creative spirit looms large throughout, as Rudd and Segel liberally indulge their inner adolescents while cementing a friendship strong enough to withstand life’s little distractions, including marriage and Sunday-night HBO.

If that makes their latest comedy sound like a page out of the same playbook that produced Superbad and last year’s Pineapple Express – aggressively silly male-bonding fantasies with a heart – you’re not far off. But Rudd and Segel, whose on-screen chemistry is one of the movie’s sublime pleasures, take what might have been a slick, formulaic exercise and turn it into the year’s funniest film to date with their unselfconscious physical humor and goofy repartee.

Rudd plays Peter Klaven, an unfailingly responsible real-estate broker with a pretty fiancée (Rashida Jones, of The Office) and hobbies that include fencing, cuddling with his girl and watching Lost. His social calendar is perpetually uncluttered thanks to his lack of male pals (the kind to be found in any respectable beer commercial), so when it comes time to recruit a best man, Peter embarks on a mission to find one.

Sydney (Segel) seems the perfect fit. He’s a good-natured layabout, wildly uninhibited and slovenly to the core, and his appeal to Peter is immediate. They bond over drinks, long walks along Venice Beach and a shared passion for Rush – the band, not the Jason Patric movie. But the key to Sydney’s allure is that he’s comfortable in his own skin. Peter isn’t, but he wants to be, and he takes after his new friend with a mixture of respect and wide-eyed awe.

All is not right in Sydney’s laid-back universe – there is a loneliness in him that’s masked by his Zen-like calm – and the two find in each other exactly they’ve been looking for. Yet their friendship is neither sickly sweet nor contrived. John Hamburg and Larry Levin’s screenplay is too honest for that, and Rudd and Segel keep their characters grounded, even as they flail away like hyperactive teenagers at a Rush concert and spar, verbally and otherwise, with Incredible Hulk star Lou Ferrigno.

Peter and Sydney’s platonic romance (sorry, I’m not using the bro word) is subtler than you’d imagine, even touching, but it’s also riotously funny. The two of them are far from conventionally cool – Peter’s attempts at casual guy talk are clumsy at best, and Sydney’s uncensored outer monologues are enough to make a strong man cringe – but they are genuinely, recognizably human, and therein lies the charm that makes I Love You, Man such an unexpected delight.