When our hero, voiced by Jason Lee, is thrown off of the police force because he mistakes the smell of ham for the smell of a bomb, he ends up becoming a laboratory animal under the care of Dr. Barsinister (Peter Dinklage, the "angry elf" from Elf) and his underling, Cad (Patrick Warburton). The doctor's goal is to extract the special abilities of various animals and make a concoction that can give its user super powers. Well, it seems the formula he uses on our beagle friend did the trick, and upon his escape, he runs into a former cop who is currently a security guard at the lab, Dan (James Belushi). Dan takes the dog home to his son and the pair name him Shoeshine.
Jack, Dan's son, soon finds out about Shoeshine's powers when Shoeshine starts talking to them. While trying to figure out the extent of his abilities, Dan and Shoeshine run into Molly (a student at Jack's school) and her dog Polly. Soon Jack and Shoeshine not only realize that they need to use the super powers to save the city, but also keep the beagle's identity a secret, and thus the rhyming hero that is Underdog is born.
Most of the movie focuses on Barsinister and Cad's attempt to capture Underdog and figure out exactly what mix of DNA cocktails gave him his powers. While that is the overarching plot, there are plenty of times when Underdog is flying about the city stopping other crimes and trying to figure out just what his catch phrase should be. As for how it compares to the cartoon, while Shoeshine/Underdog is somewhat klutzy, he is nowhere near the absent-minded, bumbling superhero portrayed in the 1960's, but maybe the updated settings and attitude aren't bad for the character.
There are quite a few features on this disc too. There are deleted scenes and bloopers (mostly film of the trainers trying to get the dogs to do their stuff) and a featurette following a day in the life of dog actors, which is a nice perspective on just what goes on for training and so on. Probably the more interesting aspect of these special features for me, though, were the two original Underdog episodes, "Safe Waif" where Underdog has to break into a bank safe to free a kid and "Simon Says" where Barsinistar has a Camera Gun that turns people into pictures. These are both great examples of classic Underdog-ness and fit really well in the disc. In fact, it really makes me want to go out and pick up the Underdog cartoons on DVD.
I have to say though, while the CG might look good on the DVD version, with the amount of detail you can see on the Blu-ray, there are some very obvious color and texture differences that pop and stand out. It's a real shame because I would say a movie with this much CG should be in high definition, but it doesn't look like the dogs' lips and heads transition quite smoothly enough into the rest of their bodies for a media like this. There doesn't seem to be much difference between Blu-ray and DVD as far as special features are concerned, and with the CG issues becoming very noticeable in high definition, while I recommend the movie (to watch at least once), I would recommend the DVD over its Blu-ray counterpart.