THE MAN BEHIND THE CHIHUAHUA

That Taco Bell canine looks as if he's really talking, but it's the work of a visual effects artist.

Michael Killen spent four days making a dog say four words. In Spanish, no less.

Granted, it was no ordinary mutt. It was a sassy, girl-crazed, junk food-scarfing bilingual dog that he found in Hollywood. But he got it to say something on TV that has become the envy of America's gargantuan fast-food industry: "Yo quiero Taco Bell."

A hip cultural icon was born. Muchos tacos later, Killen is working inside a production studio in Pittsburgh, making the Chihuahua say other things. Or at least Killen is creating the illusion that the dog is talking in Taco Bell's wildly popular advertising campaign.

Killen _ known as the "Taco Bell boy" at North Coast studio in Pittsburgh _ hasn't gotten rich or famous off the campaign. But the talking Chihuahua is a nice thing for a visual effects artist to put on his resume.

"It's been a blast, an absolute blast," said Killen, 35.

It has much harder than it looks to stretch a dog's snout. Or to widen its eyes so that it is seemingly craving a cheesy gordita. Or to infuse a scrawny dog with the attitude of a 19-year-old dude.

But Killen does it so deftly on the computer that he got the ultimate compliment: Some people, including a few reporters, wanted to know how Taco Bell got the dog to talk. Killen said some people even asked franchises, "How can we get our dog to talk, too?"

Killen makes the dog believable with subtle gestures. In the first commercial, the Chihuahua races past a swooning female dog on the sidewalk, only to stop in front of a teenage boy eating a taco. The dog tells the boy, "Yo quiero Taco Bell" or "I want some Taco Bell." Killen raised the dog's eyebrows as a punch line.

"It all comes down to the eyebrows," Killen said. "One flick of the eyebrows. That's the home run. It was like, "Wow, this dog has attitude.' "

Killen, a graphic design major at Carnegie Mellon University, was working at Post Logic Studios in Los Angeles two years ago when he first got the Taco Bell call.

At that point, Killen had done visual effects for music videos ranging from Sheryl Crow to Julio Iglesias and had made a man's skin shed in the vampire movie Blade.

But he had also racked up some pretty impressive talking-animal credentials, the rage in commercials. He had made an iguana sing for a Don Pablo's Mexican restaurant commercial. And he had made four junkyard dogs gab as they chased cars in a Ford commercial.

The talking Chihuahua led to the sale of 21-million talking plush Chihuahua toys, caused a run on real Chihuahuas and spawned wacky talking-dog Web sites. (The dog with a Spanish accent wasn't universally loved, though. A few Latino leaders said it was demeaning.)

Animals can talk now because the special-effects wizardry available on computers has improved drastically. Animals are no longer fed peanut butter to make them open their mouths awkwardly, the way they were as recently as the 1980s.

While the Oscar-winning techno-wizards for the movie Babe made a pig talk by creating geometric images on a computer screen and adding layers of skin and hair, Killen used another painstaking method.

He took two-dimensional footage of the dog, and using computer software, created a grid based on muscle shapes. He then stretched and warped the image along the mouth muscles to create the illusion of talking.

Killen enhanced the footage with painted images _ an occasional tooth or tongue thrust. For example, during a recent PepsiCo promotion for Star Wars, the talking dog joins Colonel Sanders and the Pizza Hut delivery girl in a car. The Chihuahua appears and says: "Let's do this."