Run Fatboy Run may come as a disappointment to fans of star Simon Pegg. The British actor struck gold stateside with two hilarious movies, Shaun of the Dead and Hot Fuzz, films which ended up turning the zombie and cop genres on their ears. But there's nary a hint of satire found in Run Fatboy Run. It's so weighed down by convention that anything snarky emerging from the predictable plot is swiftly crushed under the steel-toed boot of conformity.

Five years ago, Dennis Doyle (Pegg) made the mistake of a lifetime. Not ready to lead a responsible life, Dennis took off running -- and mere moments before his wedding, leaving pregnant fiancee Libby (Thandie Newton) behind him. Now, as a lowly security guard, Dennis is still paying the price, but his drastic decision is about to bite back in the worst of ways. Libby has found herself a new companion in the form of Whit (Hank Azaria), a charming American businessman who seems to have everything our slacker hero lacks. After learning about Whit's intentions to run in an upcoming marathon, Dennis decides to join the race. Why? He wants to show Libby he's ready to start growing up. The more Dennis trains for the big run, the more he realizes what a doofus he's been his whole life, and now he's determined to win back his ex's heart before her dashing suitor steals it away.

Because of the creative team behind Run Fatboy Run, I expected the results to be a lot more amusing. Pegg himself and stand-up stalwart Michael Ian Black took on screenwriting duties, while David Schwimmer (yep, the "Friends" guy) stepped behind the camera to direct. I thought it would at least find some way to break free of its weary genre roots. Instead, the story embraces them, playing out as an amalgamation of every other sports movie ever made. Schwimmer and company leave no cliche untouched, so viewers know exactly where the plot is heading at all times. Still,  Run Fatboy Run comes across as a likable movie.  There's enough scruffy charm about the picture to make it a perfectly tolerable take on the underdog story. However, the film appears afflicted by the same laziness as its lead character, seemingly lacking the desire to stray from its thematic comfort zone in order to give viewers something that's daring.

Any refreshing elements included in Run Fatboy Run result mostly from the performances. Though it's a little tiring seeing Pegg experience the full brunt of Murphy's Law for a good 90 minutes, he turns Dennis into a directionless gadabout you come to like. His reason for leaving Libby at the altar may be a bit of a cop-out -- and arrives with next to no emotional  effect -- but you still find yourself rooting for the poor lug as he tries atoning for his oafish ways. Newton is quite good here too, wisely avoiding the trappings of the sterotypical girlfriend role. Libby isn't dumb enough to accept Dennis back into her life with open arms, making it clear it's going to take a lot more than completing a marathon to earn her respect again. Run Fatboy Run begins to make progress in this department, but these good vibes don't last long, for most of the story is quickly consumed by Dennis' rather boring quest to one-up Whit, who, of course, is much more of a boastful lout than he lets on.

I think fans of Pegg's previous and edgier comedic works are in for a bummer with Run Fatboy Run. As earnest as its intentions are, this creaky film soon runs out of breath and finds itself trudging dutifully but obliviously to the finish line.

MY RATING: ** (out of ****)

(Released by Picturehouse Entertainment and rated "PG-13" for some rude and sexual humor, nudity, language and smoking.)