Shoot 'Em Up is like an old Warner Brothers cartoon, with Owen playing the role of Bugs Bunny (complete with ever-present carrot), and Giamatti playing Hertz as a mash-up between Elmer Fudd and Yosemite Sam. Each gunfight escalates the carnage and violence, much like in those old cartoons. When Bugs was being hunted and the first plan didn't work, each successive plan would get increasingly zany. At one point Owen even says "What's up, Doc?" after taking a nice and crunchy bite of a carrot, as if to drive home the point of this being a hyperactive cartoon.
Writer/director Michael Davis makes the jump from direct-to-video horror features to the big screen in outlandish fashion. Each gunfight is more inventive then the last. Davis employs only one speed throughout the brief 85 minute run — full. There are barely any moments to catch your breath. These slowed down moments are only used to propel the thin story forward. When it comes right down to it, this movie has no interest whatsoever with story. It is about body count and outlandishness. The script is peppered with one-liners, and little character development.
Bottom line. As shallow as the script is, as thin as the story is, it all works. The energy that Davis injects, the cool factor of Owen's performance, and Giamatti's scene-chewing all add up to one absolute blast of a movie. It is pure satire, taking aim at action movie conventions, and even tossing in some anti-gun messages to boot. However you look at it, this is a nonsensical film that is held together by the charismatic performances and the over-the-top action.