Run, Fat Boy, Run comes from a background of comedy gold, three times over: the off-kilter quirkiness of writer Michael Ian Black, the sweet goofiness of director David Schwimmer, and the British everyman humor of cowriter and star Simon Pegg. Ideally, the film would have joined the three comedy styles seamlessly, creating a lovable, hysterical movie that could do no wrong.

Unfortunately, Run, Fat Boy, Run feels like three different movies as disparate as its influences: one set of gross-out jokes that would make the Farrelly Brothers proud, one sweet but schlocky romantic comedy, and one laugh-out-loud underdog story. It's as if the trio couldn't commit to just one sort of film, bouncing from saccharine father-son scenes to disgusting blister-popping to Pegg's trademark loser-y antics. The result is a film that isn't bad, just disappointingly ordinary.
Pegg stars as Dennis, a man who chickens out on his wedding day and runs away from his pregnant bride, Libby (Thandie Newton). Five years later, he wants to win her back — but Libby has started dating Whit (Hank Azaria), a slick American stockbroker who seems to be good at everything, including running marathons. Dennis decides that the way back to Libby is beating Whit at his own game and decides he, too, will run a race. Never mind that just running down the block leaves him winded; he's going to finish 26.2 miles and get the girl, to boot. Things follow a fairly expected path from there — though there are some laughs along the way — so read more