If Mark Walton weren't a real person, his appearance -- gangly frame, shiny dome, bushy beard, broad smile and mischievous eyes -- would make the good basis for a cartoon character.

That's appropriate, since cartoons have been a constant in this East High School grad and Utah State University alumnus' life.

"I always knew I wanted to draw in some way, shape or form," Walton said in a recent interview.

But while Walton, 40, is a veteran artist at the Walt Disney Studios -- as a story artist whose credits include "Tarzan" and "Chicken Little" -- he has become an unlikely animation star for something else: His voice.

Walton is the breakout voice performer in Disney's new computer-animated adventure, "Bolt," opening nationwide today. The movie tells the story of Bolt, a dog (voiced by John Travolta) who plays the star of a superhero action TV series -- only the dog thinks he really has superpowers. Walton provides the voice of Rhino, a hyperactive hamster who is Bolt's No. 1 fan, and eagerly joins the dog on his cross-country adventure, rolling along in his plastic hamster ball.

Walton's second career as a voice actor started accidentally. While working on the movie "Sweating Bullets" (which was later retitled "Home on the Range"), Walton got to write a few scenes. In describing one scene, Walton performed some of the characters' voices.

"They liked the way I read the lines when I was pitching my scene," Walton said. That's how he ended up giving voice to two amorous bulls, Barry and Bob.

After that, Walton was asked to record "scratch" tracks -- temporary voice dialogue -- and sometimes his voice would end up in the finished film. "A lot of it is just managing to stay at Disney for a dozen years and getting to know a lot of people," he said.

With "Bolt," Walton said the directors "thought it would be funny if [I] did the hamster." So Walton recorded some "scratch" dialogue, always expecting a real actor would be hired to play Rhino.

"At some point, people started asking, 'Is somebody else going to do the voice?'" Walton said. "It was finally decided, after some deliberation, that they would keep me in the movie."

Walton has been working at Disney since he got an internship there in 1995. Usually he works as a story artist, which he describes as the second or third step in the animation process. After a director has an idea for an animated movie, he or she starts developing the movie's look with visual development artists. "At some point -- sometimes right away, sometimes a few months down the road -- they'll bring story artists on, when the story is a little more fleshed out, to start drawing out the scenes, figuring out the dialogue and the staging," Walton said.

It's an exciting time to work at Disney, as the animation studios have a new boss: Pixar head honcho John Lasseter.

"We've made Disney into a filmmaker-led studio, which is what Pixar's always been," Lasseter said in a phone interview. "Quality is the best business plan. You have every chance to make it right. We're just dedicated to that."

Walton is already at work producing storyboards for another Disney movie, "King of the Elves," which won't hit theaters until 2012. For the moment, though, he's enjoying the "Bolt" experience.

"Being in the movie at all is fantastic," Walton said. "It would be pretty exciting to have a Rhino toy, or action figure, or backpack, or anything."

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