The movie gets off to a good start, but it quickly becomes something of a letdown—especially with the awkwardly inserted 'gag reel' at the very end. *Underdog* is an amiable enough film, really a blameless 81-minute diversion. As mentioned, it does show some initial promise. I appreciated how Peter Dinklage and Patrick Warburton were presented, and the introduction of the dog isn’t as clumsy as it might have been. There are other things to appreciate too; for instance, the visual effects involving Underdog are well done, and his fast-paced dialogue that relies on rhyme surprisingly manages to be effective. Still, it's ultimately weighed down by a dull plot and its handling. As I watched, I found myself losing interest in the story and also feeling detached from the superhero dog—the novelty fades quickly, even for such a brief movie. The final part is also quite lackluster. I wouldn’t say I strongly disliked it, though. It's simply an unremarkable film released by Disney in 2007.

Source on TMDB