Run Fatboy Run isn’t exactly an underdog that accomplishes big feats. That’s just what it’s about. What it has that recent heavily promoted comedies like Walk Hard and Semi-Pro do not is likeability. A movie where an out-of-shape single dad, Dennis, joins a marathon to compete for the affection of his ex-fiancee only sounds less thrilling when you learn it’s directed by former Friends star David Schwimmer. But star Simon Pegg respects audiences’ optimism by not being afraid to portray Dennis as a loser hoping to be reborn. Having chickened out of his marriage to Libby (Thandie Newton), leaving her in tears on her wedding day, Dennis decides to fix past mistakes. No longer running away from life, he’s now trying to catch his breath. It’s a predictable sport story, but invested with feeling so that the uplift rides on big laughs.