PASADENA, Calif — They say you should never work with children or animals, but they shouldn't say that to writer/executive producer of the new Animal Planet sitcom "Beware of Dog."

After spending the past quarter century working on shows like "Magnum, P.I." "Knots Landing," "The Scarecrow and Mrs. King" and "Knight Rider," Rob Gilmer couldn't be happier that the star of his show is a dog named Chip.

"It was an amazing experience to work with him — the way he took direction, the way he listened, the way he worked with his trainer," Gilmer said. "And it proved to be the case when we got him on set. . . . I would count Chip among the easiest of the actors I've ever worked with.

"He didn't once ask for a bigger trailer. He always showed up on the set. So he was great, beautifully trained and a delight to work with."

And, obviously, you can't say the same about all human actors.

Chip (a mixed bearded collie) plays Jack in "Beware of Dog," which premieres Tuesday at 6 and 9 p.m. on the Animal Planet cable channel. He's a "con dog" who sort of weasels his way into a human family. He's a dog with an attitude — a "street-smart mutt who's looking for a place to play for about a week" and ends up staying.

Jack doesn't exactly talk, except to the audience — we hear his internal thoughts, voiced by actor Park Bench.

"I asked (trainer) Roger (Schumacher) to make the dog talk and he couldn't — about the only thing he couldn't make the dog do," said Gilmer, who added that scripts were tailored to Chip's strengths.

Before they began shooting, the writers talked to the trainers to see what the dog could do. And, as a result, the pilot episode includes Chip riding a skateboard.

"I didn't imagine in my wildest dreams that we could get a dog on a skateboard," Gilmer said, but the trainers taught him the stunt "in about three or four days."

"And I must say, I tried to do the same thing, and I couldn't do it as well as he could."

Schumacher rescued Chip from an animal shelter in 1997. He goes into the shelters looking for "dogs that come up to me — they don't sit back really scared. And in Chip's case, he was bouncing up in front of the kennel."

The trainer estimated that for every 15 dogs he picks up from an animal shelter, only one or two can be trained as performers. (The others are placed in good homes.) So Chip is one of the elite.

Not that he was an immediate success. On audition after audition, Chip "wasn't the right type" — a refrain heard by countless actors. He did get some work — he was the "back-up dog" on the TV movie "Annie" and the theatrical film "The Grinch" — but "Beware of Dog" is his first starring role. He was the first of about 30 dogs that auditioned for the producers, and the one they kept coming back to.

"I think everybody that was there that day agreed that not only was he a beautifully trained dog, but there was something — and you can see it on the screen — about Chip's face," Gilmer said. "Something in his eyes, in the way he smiles, that is so completely engaging that we all fell in love with him immediately."

And it's a love affair that continues.

"I think he was the main ingredient in making this one of the most pleasant sets I've ever worked on because he was such a great presence," Gilmer said. "He really brought a lot to the show."

IT'S ALL IN THE WRITING: Unfortunately, "Beware of Dog" isn't as good as its star — cute dog, lame show.

Like talented human actors, Chip can only be as good as the script. And the script is weak at best.

Cuteness and talent can't make up for bad writing.

"Beware of Dog" looks like the low-budget sitcom it is. It's certainly not objectionable, and the dog is appealing, but — even during a period that's not exactly a golden age of TV comedy — this looks and feels like cheap programming.