Here's an odd duck of a comedy - and I don't just mean that's how "Run, Fat Boy, Run" usually plays.

It's an awkward British thing - part broad Mr. Beanish silliness, part heartfelt character humor, with some halfhearted tweaking of sports movie cliches thrown in for good measure. It's directed by, of all people, "Friends" star David Schwimmer.

The film began as a New York-set script by "Reno: 911's" Michael Ian Black. But when financing finally came through, it was from English sources who insisted that the film be shot in London.

Schwimmer got his pal, Simon Pegg, to rewrite the piece with a Brit sensibility. Talented as he is, Pegg - who co-wrote and starred in the brilliant genre satires "Shaun of the Dead" and "Hot Fuzz" - couldn't bring this formulaic hodgepodge up to his usual standards.

Pegg plays a not-so-chubby loser, Dennis, who left his pregnant girlfriend Libby (Thandie Newton) at the altar. It wasn't so much cold feet as realizing that he wasn't good enough for her. But five years on, Dennis is still hopelessly in love with Libby and their son, Jake (Matthew Fenton). He remains an out-of-shape screw-up who can barely do his security guard job at a women's clothing store and can't make the rent on his crummy apartment.

Enter Whit (Hank Azaria), a successful American businessman who sweeps Libby off her feet and threatens to take her and Jake far away to Chicago. Fit Whit is running the London Marathon, and Dennis somehow gets it in his head that if he can go the 26 miles, too, he'll prove himself in Libby's eyes.

Through most of the movie, most sane people will root for Dennis to fail. Whit is in every way a better man (I won't give away the key revelation, but it feels mechanical), and the lovely Libby deserves the decent life he can give her that Dennis clearly can't. Still, we're expected to be on the unlucky guy's side; try as he might, Pegg rarely convinces us that Dennis' charm and newfound sincerity counterbalance his many character deficits.

Mismatched though their sensibilities may be, Pegg, Schwimmer and Black are all funny guys, and "Fat Boy" certainly boasts a couple of worthy chuckles as a result.

Directing-wise, Schwimmer takes advantage of London's many architectural niceties - this is the best-looking comedy since, well, "Hot Fuzz" - and stages both the physical gags and more emotion-based comedy well enough for a first-time feature helmer.

But the material isn't any more inspired than the protagonist is inspiring. "Run, Fat Boy, Run" should have been whipped into better shape before the starting gun sounded.

Bob Strauss (818) 713-3670

bob.strauss@dailynews.com

review>

RUN, FAT BOY, RUN

>PG-13: nudity, language, sexual situations, minor violence.
>Starring: Simon Pegg, Thandie Newton, Hank Azaria.
>Director: David Schwimmer.
>Running time: 1 hr. 37 min.
>Playing: Area wide.
>In a nutshell: London loser tries to win back the mother of his child by entering a marathon he's not in shape for. About as funny as it sounds.