''Good Boy!'' is an affecting, hot-buttered slice of toasted ''E.T.'' with a smidgen of ''Benji'' thrown in just because. A talking dog stands in for Steven Spielberg's homesick space alien, and the movie even threatens to become philosophical, with its sci-fi assertion that canines run the universe and people just don't know. But all it wants is to reduce you to mush, which I'm happy to say it does.
John Hoffman wrote and directed the movie, and what sets it yards apart from lesser family flickery is a refusal to equate innocence with naivete. The story is told mostly through the eyes of Owen (Liam Aiken), a sensitive, suburban 12-year-old who has an uncool tenderness for dogs and the cosmos. While the other kids -- represented here by two white bullies, dressed as gangstas, and Connie (Brittany Moldowan), their more tolerant black sidekick -- are playing catch, Owen is gazing at the stars and running a dog-walking business. Every day he slips into a pair of red coveralls and parades around his neighborhood's pets, proudly picking up after them.
The dog-walking business is nice, but what he really wants is a pet of his own. And in spite of the hesitation of his relocation-mad parents -- ''SNL'' alums Molly Shannon and Kevin Nealon, on their best behavior -- he gets one, even though their umpteenth move is weeks away. Owen names his pup Hubble, which is funny because he turns out to be a satellite. A turn of freak events allows Owen to hear Hubble talk. And in Matthew Broderick's voice, Hubble explains that he's been sent to Earth from Dog Star Sirius on a reconnaissance mission to find out whether it's true that humans are keeping dogs as pets.
He's appalled to learn that Owen's four canine clients -- whose voices Owen can now hear, too -- like to be walked. They're a disgrace to the race. Hubble has to whip them into ferocious shape before the Greater Dane (voiced by Vanessa Redgrave -- who else?) shows up and takes every dog on Earth back to Sirius to be retrained. But eventually, Hubble's disgust for domestication (''if one more person wipes his hands on me . . .'') turns to enthusiasm: He really wants to learn how to fetch.
''Good Boy!'' can be crass (more than one dog is a little gassy), but it's also quietly progressive: Wilson, the boxer, belongs to the gay couple down the street. And in its final scene, the film is touchingly firm about leveling with children, drawing a careful, crucial line between fantasy and reality, without patronizing or haranguing them.
Aiken probably wouldn't stand for condescension, anyway. Through his uncannily vivid face, we see a boy's already expansive world open up even more. When the Greater Dane arrives and the dogs might have to leave forever, the boy's heartbreak is yours.
And darned if Owen's complicated love for his Hubble isn't as tear-jerking as Barbra Streisand's love of the one Robert Redford played in ''The Way We Were.'' Call it far-fetched, if you must, just don't call it puppy love.