Peter Chelsom’s “Serendipity” has all the usual romantic comedy trappings: a guy; a girl; goofy best friends; and most of all, that special something, that fairy tale quality. In other words, it’s fluff. But with the help of a diverse and charming cast, “Serendipity” pulls off its own fortunate accident and manages to become an enjoyable bit of brain candy.

“Serendipity” immediately creates a world of fantasy; it is Christmas in New York, and Ray Charles sings throatily in the background. Even the title fonts have a certain whimsy to them. Everything’s going normally until John Trager (the perennially cute John Cusack) and Sara Thomas (Kate Beckinsale) grab the same pair of cashmere gloves at Bloomingdale’s. Instantly there’s something in the air, and it ain’t snow.

Sparks fly, and John and Sara end up at the latter’s favorite cafe, which shares its name with the film. Sara loves the word “serendipity” even though she has an obsessive belief in fate. When the time comes to exchange numbers, Sara writes hers down (after much convincing by John) only to have the wind blow it away. This, to Sara, is a sign that they are not meant to be.

Instead of sticking to her lofty ideals, Sara devises a plan to give fate a bit of assistance. She and John agree to write their phone numbers in a used book and on a five-dollar bill, respectively, in hopes that the book and the bill will find their way to the other person. Of course, neither Sara nor John leaves their future relationship completely to fate; their searches for each other take up the rest of the film’s brisk 90-minute running time.

No romantic comedy can be without its cliches, and “Serendipity” definitely has them — pointing out constellations, ice skating at Rockefeller Center, a cheesy soundtrack that only redeems itself with Nick Drake. But this film takes one classic romantic comedy subplot and exalts it to an entire film — the infamously annoying “near-meeting–when-the-main-characters-just-miss-each-other-even-though-their-entire-affair-depends-on-their-meeting-right-then” (or so we are led to think). Meg Ryan and Tom Hanks lifted it into an art form in “Sleepless in Seattle” and “You’ve Got Mail”.

The device normally serves to fill out running time a bit better or to increase tension. Usually it’s just frustrating and “Serendipity” is no exception. Each near-meeting does show that John and Sara are meant to be together, but this film uses the technique ad nauseam. At one point, Sara even sticks her finger in John’s used gum, stuck to the back of a bench he sat on days ago — no doubt, this represents a deep, sticky cosmic connection.

Cusack and Beckinsale have charm to spare, however, and they manage to pull off the heavy-handedness. Cusack has long since left behind his bumbling teenager days — so accurately captured in “Better Off Dead” and “Sixteen Candles.” Though pieces of his gawky charm still peek through, he has shouldered the Romantic Lead type quite well. It isn’t unfamiliar territory, after all. Who doesn’t remember Cusack holding that boombox above his head playing “In Your Eyes” to Ione Skye in “Say Anything”?

Dropping the “Pearl Harbor” American accent, Beckinsale’s clipped British accent is as fresh as she is. Sara is much more likeable than the maudlin nurse Beckinsale played in her last film. There are no contrivances or lofty intentions to her performance — it is simple and pure even though Sara is a head-over-heels romantic.

A host of supporting characters bolsters the film as well, blurring problems of plot. Molly Shannon and Jeremy Piven are the best friends — loyal and slightly zany. Piven writes obituaries for the New York Times, while Shannon owns a new age store but hates anything remotely ethereal. Shannon lets her own personality shine through her cynical character, allowing for some slapstick comedy and goofy, awkward moments. Also interesting, to say the least, is Sara’s would-be lover Lars (John Corbett of “Sex and the City”), a goofier, musical version of Steven Seagal, complete with Orientalist aesthetic.

During his few minutes on screen, Eugene Levy — veteran of “Waiting for Guffman” and the “American Pie” films — simply lights it up. Playing an anal sales clerk who eventually helps John in his search for love, Levy again nails the small-town, ordinary guy who thinks he’s a big man.

The cast and the upbeat tempo of the film make up for plot problems and not-quite-funny writing. (“How does Bora Bora sound to you?” — “Sexy sexy.”) The action follows John while cutting often to Sara, heightening expectations and building to John’s ill-fated wedding. The film does not stop for mush, getting preachy only when necessary to drive home that concluding fairy tale lesson (that is, they do come true).

“Serendipity” has to fight the battle of all romantic comedies, which is to make a modern adult audience believe in fairy tales, if only for 90 minutes. With its contrived plot, the film should be doomed to dullness and considered too transparent to provide even modest entertainment. Nonetheless, fate also blessed “Serendipity” with a cast of likeable characters and actors. If you don’t wholeheartedly believe in fairy tales and soul mates by the end of the film, at least you want to believe it for the sake of Sara and John.

Serendipity, showing at:

Showcase Cinemas North Haven (234-8000), Hoyts Branford 12 (481-2711), Showcase Milford (878-5600).