Sick puppy. Mongrel. The dog's dinner. Pick the most derogatory canine expression you can think of and it will apply to this remake of Disney's 1959 The Shaggy Dog, which spawned a 1976 sequel, The Shaggy D.A., starring the redoubtable Dean Jones.

Whatever your assessment of Tim Allen's capacity for physical comedy, becoming a dog is a feat no actor should attempt. It's akin to the old theatre adage about not working with children or animals because you'll always get upstaged. Many respected performers have done humiliating things on camera for a laugh. But you better get a laugh.

Fred MacMurray was smart enough to play the father of the boy transformed into a dog in the original. And Jones was probably forced to play that boy as a grown-up in the 1976 sequel since he was overdue for another hit in a Mouse House vehicle.

This update seems to have been made on the cheap and neither its genetic nor its plot mutations are funny. Much of the problem stems from a set-up that's far too complicated. We begin with the snatching by paramilitaries of a miraculously long-lived Tibetan hound somewhere in the Himalayas. Aging 1 year for every 7 human years, he embodies the fountain of youth and a maniacal scientist (Robert Downey, Jr.) from an American drug company wants to bottle the secret. 

Back in Los Angeles, Allen's deputy district attorney is charged with prosecuting an animal rights activist who set fire to the company's lab to protest their experiments. The crusader happens to be a teacher of the lawyer's daughter, and she believes in the cause and nags her Dad to drop the legal action.

Through sheer coincidence he's then bitten by the dog, which results in such involuntary behavior as growling, fetching and raising one leg at the urinal. His sense of smell and hearing are greatly enhanced. Allen could have drawn on memories of his salad days for these scenes. It's like he's tripping. It's a bad trip from where we're sitting however.

His plight is made thornier by the fact he's a workaholic and has been neglecting his family, which includes a wife (Kristin Davis) and a son whom he pushes to play football. Naturally, seeing life from a dog's point of view makes him a better father and husband.

The transitions between human and dog are poorly done. At certain inexplicable moments he's a lawyer with dog traits and then suddenly he turns into an actual dog, with Allen providing voice-over. It's unclear what triggers the metamorphosis and shots of his suit crumpled on the ground, or the bare actor wrapped in a towel after snapping back into human form, look amateurish.

Expectations of a cute, cuddly and silly movie are quickly dashed. Yet not only is The Shaggy Dog loud and irritating -- bring earplugs for the inevitable blaring of "Who Let the Dogs Out?" -- it has a nasty, Kafkaesque side. The company scientists create a menagerie of mutant fauna (for example, a half bulldog-half frog and a snake with a dog’s tail) and Downey's villain, who relishes torture, puts his boss in a coma.

Forget animal rights, who's safeguarding the dignity of the supporting actors, including Danny Glover and Jane Curtin? Hasn't the talented Downey repaid his debt to society? He has now. He and Allen's courtroom growl-off is excruciating. Kristin Davis never had a boyfriend or mate this beastly on Sex in the City.

Adding insult to injury, the filmmakers include a reference to Allen's turn as Buzz Lightyear in the Toy Story movies. The only possible correlation between Buzz's catchphrase "To infinity and beyond" and The Shaggy Dog is if he's referring to a trip to the pound. Even the most loving family would put this mutt to sleep without thinking twice.

(Released by Walt Disney Pictures and rated "PG" for some mild rude humor.)