The movie opens on the wedding day of one Dennis Doyle (Simon Pegg), who, faced with the prospect of a lifetime commitment, turns and runs, leaving his pregnant fiancé, Libby, at the altar. Pick up five years later, when Doyle is a bum of dad living in a basement apartment when he isn't an ineffectual security guard at a lingerie store. For him, this is apparently a satisfactory arrangement — until Whit (Hank Azaria), a successful financier, arrives to sweep Libby off her feet. Suddenly jealous, Doyle vows to win back the woman he jilted by showing he can do anything Whit can do — including running a marathon. Unlike five years ago, he just has to hope this time he's running in the right direction.

I'm not above "stupid humor" (I highly recommend Dude, Where's My Car?), but it's not what I was hoping to find in Run Fat Boy Run. As such, the first half of the film was disappointing, laden as it was with puerile jokes regarding body parts and fluid. But about halfway through, Doyle suddenly realizes that this race isn't a joke, and that there is in fact something important at stake. What we're then given is a film that loses none of its lightheartedness as it shifts its focus from simple comedy to being about priorities, introspection, family, and amends.

Most important, the film emphasizes not just the physical demands of running a marathon, but also the mental challenge. There's much more to running than just putting one foot in front of the other — if there wasn't, anyone could do it, and anyone can't. Doyle encounters some significant obstacles in his path not just to the finish line, but also to the starting line, and whether or not he surmounts these hurdles, the film makes his abilities, limitations, and decisions entirely believable.

I've been avoiding Simon Pegg films, wanting my first exposure to the actor to be his portrayal of Scotty in the upcoming Star Trek film. I broke that abstinence this past Halloween when I succumbed to the thoroughly enjoyable Shaun of the Dead. In both comedies, Pegg plays a character that has a surprising degree of authenticity, which encourages my faith in his ability to play more serious roles. It's like watching Will Ferrell's evolution from Elf to Stranger than Fiction, or Jim Carrey from Ace Ventura to The Truman Show.

Though Hank Azaria first registered on my sensors due to his work on The Simpsons, he's since made a name for himself apart from his voice work with movies like like Godzilla and Tuesdays with Morrie. In Run Fat Boy Run, he initially comes across as a perfect American — fit, friendly, and financially sound. But his mature appearance hides an insecurity that eventually bubbles to the surface, presenting a balanced contrast to Pegg's own character development.

The more I think about this film (especially its latter half), the more I like it. Although the presence of the marathon suggests a situational comedy, Run Fat Boy Run ultimately a character-driven one, which is an essential ingredient to any critically successful film. I would've had a hard time seeing this movie in theaters, since I occasionally relied on the DVD's subtitles to translate the British accents, but I can wholeheartedly recommend it to anyone willing to put up with some potty humor on the way to something more sincere.