Run Fatboy Run

As John Simon once said of Jeanne Moreau — cast in a virginal role — making Simon Pegg a fat guy is like casting Lassie as a vegetarian. Take Chris Elliott, subtract Don Knotts: the remainder is Pegg, the British actor-screenwriter who barely registered as an appetizer for Shaun of the Dead's ravenous ghouls. Even outfitted with a modest little baby-bump of a gut, as in the new comedy Run Fatboy Run, he's the scrawniest pear in a drought-stricken orchard. Simon Pegg is fat like Iceberg Slim was white.

Presenting the slight Pegg as an out-of-shape security guard who goes on a quixotic quest to train for a marathon — in three weeks' time — is a pretty good joke in itself, given the casting predilections that govern the movies these days. Not long ago, fat comics had a niche all their own. Their leads might have been few and narrowly tailored, but like zeppelin pilots, they'd learned to maneuver their bulk with dexterity. These days, why hire someone who actually eats, God forbid, when you can bury Gwyneth Paltrow, Eddie Murphy or John Travolta under pounds of latex? Were he alive today, that great gust of appetite Zero Mostel still wouldn't get anywhere near the movie of Fiddler on the Roof. They'd just drape a size-54 peasant jacket over Adam Sandler and crank up the foam-insulation blower.

None of which, of course, is Pegg's fault. The audience has expressed its preference for Martin Lawrence in Big Momma's House over Mo'Nique in Phat Girlz, for the easily reversible illusion of fat over the hard-to-handle reality — something fat comics understood and accounted for, inflating their personalities into human balloons. And in his cheery, lightly subversive way, Pegg sympathizes. Run Fatboy Run, which he co-wrote with Stella's Michael Ian Black, is not about a figure of Sherman Klump-like obesity, but about an average guy who's been psyched out by the standards of perfection around him. He'd count as a real porker only in Hollywood.

Pegg's Dennis has never lived down the day, five years earlier, when he made a feverish 500-yard dash away from the altar (and his pregnant bride). The weight of that decision bears literally on him: He's now a paunchy watchman at a posh lingerie shop, reduced to huffing and puffing after a tease of a trannie shoplifter. When his still-smarting ex, Libby (Thandie Newton), takes up with an appalling overachiever — a wealthy American fitness nut with a passion for long-distance running — Dennis wakes from his ever-say-die funk to declare he'll run the same upcoming race as Mr. Right.

And so inspirational sports-saga conventions hit the starting line alongside romantic-comedy cliches, with the quicksilver Newton reduced to playing that wheeziest of parts, the woman who's measured by her tolerance for the hero — a task that has hamstrung every predecessor from Sally Field in Mrs. Doubtfire to Maura Tierney in Liar Liar. As in those movies, the hero's been given the unquestioning adoration of a child (open-faced little Matthew Fenton), while his rival (Hank Azaria, oozing self-satisfied smarm) is made only perfect enough to let the hero's imperfection gleam in comparison. Granted, what flab Run Fatboy Run has comes mostly from these adipose prefab elements, which play out exactly as they have in a hundred earlier movies.

But Pegg, here and in his surprise hits Shaun of the Dead and Hot Fuzz, has staked out a peculiar slant on genre material that ventures beyond irony toward rehabilitation. Pegg's melancholy in these familiar settings seems more keenly felt than a plot convenience. There's nothing hoarier than the old it's-not-you-it's-me gambit that dashes Dennis' wedding, but Pegg's flop-sweat agony, though finely calibrated as slapstick, convinces us that he really doesn't feel worthy of Libby (and honestly, so does Newton). It takes Azaria's smirk of entitlement to make Dennis disprove what he himself believes — that he's too pudgy and foolish to deserve this woman.

Pegg seems to regard genre conventions as something like rules for living: Use them as workable guidelines, like track lanes, but sprint at your own speed. His movies to date are about people in genuine danger of ending up alone — people susceptible to the appeal of a uniform, reductive society (the undead, Hot Fuzz's village-green star chamber) even if they're pulled back to safety by the comfortably flawed (represented here by Dennis' best friend Gordon, played by the hilarious Dylan Moran, a dissolute dandy who sloshes through life like Dean Martin ogling starlets).