In demand British comedic actor Simon Pegg stars as Dennis, an immature, irresponsible, and out of shape single father who has been trying to make amends for leaving his pregnant bride to be Libby (Thandie Newton) at the alter 5 years ago.

When Libby begins dating a well off American financial consultant named Whit (Hank Azaria), Dennis intends to show him up and win Libby’s heart by completing the famous Nike River Run marathon under the guidance of his best friend Gordon (Dylan Moran). Cue a training montage featuring Pegg in the tightest short shorts this side of a gay parade! 

Considering the talent involved, Run Fatboy Run should have been much better. Friends star David Schwimmer takes on directorial duties (no doubt to branch out after playing the same role for so many years), and while his direction is adequate, Schwimmer’s  inability to take risks with the material handed to him leaves the film languishing in clichéd sports movie schmaltz.

Even the hilariously spirited fight scene between Pegg and Moran comes off as repetitive, considering that Colin Firth and Hugh Grant did it much better in Bridget Jones’s Diary.    

What keep’s the movie from drowning in its stock filmmaking are the performances. Pegg proves he can survive without his Hot Fuzz cohorts Nick Frost and Edgar Wright by his side, injecting humour and a loveable clumsiness to a character - aptly described as a “cock” by one elderly lady - who is introduced not doing the most chivalrous of deeds.

However, the best laughs come from Irish comedian Dylan Moran, who steals every scene with his sly wit and dry delivery. Also, a cameo from Little Britain’s David Walliams is a highlight.         

At its heart, Run Fatboy Run is a film about redemption and responsibility. Some of the humour on hand can be rather crass and immature, but the performances from Pegg and especially Moran will insure a few laughs.