A genetically mutated dog with superpowers must save his family and his city from the man who created him. When a police dog sets City Hall into a panic when he begins sniffing some boxes near the mayor, and it turns out he wasn't sniffing a bomb, just some ham, the dog runs away from the force, left alone in this world. Then, a big lug named Cad grabs him and takes him to the lair of his boss, Simon Bar Sinister. Simon and his genetic experiments were rejected by the city, and he has sworn revenge against the lot as a result. He injects a serum into the dog, hoping to give him powers, but when the dog wrestles free, runs around crashing into things in Simon's lab, exposing himself to all manner of other creations Simon has cooked up in his lab (chemicals, lasers, etc.), he suddenly is able to smash through a metal door and run free. Simon and Cad know that their serum was a success... but the dog is gone. Meanwhile, the dog is hit by a car (which hurts the car more than the dog), and the driver of the car, Dan, takes the dog home to his son Jack. They name the dog Shoeshine and leave him at home, unaware that Shoeshine's powers grow stronger and he inadvertently causes a huge mess in the house. When Jack returns, Shoeshine apologizes, and they realize that Shoeshine has the ability to talk to humans. Jack and Shoeshine grow close, and they even find matching love interests in a young girl named Molly and her dog Polly. When wanting to foil a robbery by Simon and Cad, Shoeshine puts on a disguise and takes on the name of "Underdog." Simon can't find the right combination of his chemical creations that led to Underdog's powers, so they decide to take Underdog's DNA, kidnapping Dan and Jack as a means of getting Underdog to consent. Simon then makes pills that will give superpowers to whoever takes them, and he makes antidote pills for taking them away-- especially for giving to Underdog. Underdog takes the antidote, and Simon gives three huge German Shepherds superpowers to carry out his evil plans to blow up a bomb that will spray mind control liquid all over the city. In a scuffle with Simon, Shoeshine rips open his pockets and a super-pill falls out, making him once again Underdog. Simon takes some of his own pills, giving him powers, but after Underdog convinces the German Shepherds that Simon is a bad owner, they restrain him long enough for Underdog to bury the bomb, neutralizing its impact. After, they go back to their lives, and Underdog remains the city's protector.
Best part of story, including ending:
It's a fairly generic film with mediocre special effects, and it certainly lacks the wit and heart of the original cartoon.
Best scene in story:
Peter Dinklage is a strong scenery-chewer, so when he gives himself super-powers, it's fun watching his evil reach new heights.
Opinion about the main character:
Shoeshine/Underdog is the blandest hero imaginable. There have been plenty of movies with strong dog leads-- this isn't one of them.