See Spot Run (2001)

Gordon Smith, (David Arquette) is an offbeat mailman who has never met a dog he couldn't handle. When he offers to baby-sit James (Angus Jones), the young son of his beautiful neighbour Stephanie (Leslie Bibb), he's hoping she'll return his romantic interest.

A hard working single-mother, Stephanie thinks Gordon is just an overgrown kid himself but circumstances force her to leave James with him, temporarily, while she is away business.

Meanwhile in another part of town, an FBI agent named Murdoch, (Michael Clarke Duncan) is trying desperately to find his runaway canine partner, Agent Eleven (Bob the dog) who has escaped from protective custody.

Thanks to the super dog's drug detecting abilities, he has incurred the wrath of local mobster kingpin Sonny Talia (Paul Sorvino) who has put out a contract on the four footed fed. Luckily, Agent Eleven is a lot faster and smarter than Talia's two inept henchmen Gino (Joe Viterelli) and Arliss (Steven Schirripa), so they aren't having much luck. They lose the trail completely when the dog seeks refuge in Gordon's mail truck, where he is promptly adopted by James, who names him "Spot."

Gordon is not exactly a dog lover, especially after having to use his ingenuity to fight off the mailman-hating mutts on his harrowing Bleeker St. postal route. Armed with a variety of ingenuous devices, Gordon enters the combat zone and emerges victorious, if not exactly unscathed. Back at the post office, his colleague and good buddy Benny (Anthony Anderson) is always ready to commiserate and offer advice to Gordon about his job and his love life.

Meanwhile, Stephanie is having her own set of unbelievable adventures trying to get back home, thanks to a freak snowstorm. Spot appears to be nothing but trouble so Gordon tries to persuade Angus to give him up. Instead he finds both the kid and the pooch beginning to grow on him.

When the mobsters catch up to them at the local pet store, all heck breaks lose. As the fur, fish and feathers start to fly, Spot finally gets to show his true colors. By the time Stephanie returns home to find her son and Gordon remarkably transformed, Agent Murdoch has shown up to reclaim his dog. The final decision is up to Spot but the lives he has touched will never be the same.