Little is asked of talking-animal movies, save charm, heart, and at least one scene where said animal wears a lampshade. Good Boy! has all those things, plus a winning story line: Hubble, a prickly Benji-like alien voiced by Matthew Broderick, lands on Earth and is shocked to see his terrestrial cousins (actually estranged colonists from the Dog Star Sirius) reduced to pets. Assisted by sweet, lonely Owen (Liam Aiken), a kid who learns to speak dog, Hubble prepares the planet's pooches for the coming of the Greater Dane (Vanessa Redgrave -- her coat has never looked glossier). One caveat: ''Boy'' contains a canine huffing scene that makes household inhalants seem benign -- though it's oddly suited to a film where Brittany Murphy voices a nervous whippet. Her ticks are priceless.