Rhino the hamster posed the most unique problems. To find the best-looking designs, the team created "paloozas," a creative refining process that transformed Disney's workflow system.

"The trio of characters really plays off each other emotionally and dynamically," Howard continues. "We knew that since John was our boss and his standards are so high that our animators wanted to live up to them and exceed them. The nice thing about John, too, is that he is such a film fan. The opening action sequence, for example, was important to show what Bolt has experienced every day of his life for five years and where his head is. And John told us that it has to be the craziest, over-the-top action sequence that anyone has ever seen in an animated film. And so we really tried to do our homework and study action and rise to the occasion. And we threw everything at our technology team. It's not a small film by any means. It's got just a few main characters, but it has a vast scope and they go across the country and there are explosions and helicopters and tons of different sets and all these problems to be solved. And they knocked them all down [with the help of Visual Effects Supervisor John Murrah, who's worked with Michael Bay]."

Meanwhile, for the character animators, the challenges of Bolt meant creating a completely new working method. While Bolt is the lead character, Rhino posed the most unique problems. The first thing was to make the character look appealing. To hone in on the best designs, the team created something called "paloozas," which are a creative refining process that began with a successful "Boltapalooza" (for the dog) and progressed to "Mittenspalooza" (for the cat), "Pennypalooza" (for the human girl) and "Rhinopalooza" (for the hamster). The team also underwent an enormous change in workflow. Instead of moving from modeling to rigging to animation, which would then go back and forth for approvals, and could cause huge problems if a rigging change was required, they worked more collaboratively. There was the formation of a character team that worked interactively, starting with modeling and moving to rigging and then to animation, but proceeding back and forth in a fluid, circular motion. This system has proved so effective that the change in workflow has become the new standard at Disney.

As for Rhino, the animators turned to squirrel designs from Sleeping Beauty (stylized but anatomically correct) for inspiration. "Rhino was originally rigged as a quadruped, and worked very well that way," explains Clay Kaytis, the Rhino supervisor. "But the story demands really said that he needed to stand on two legs and act anthropomorphically. Of all the animals, he was definitely the most human in acting. And it was such a struggle to get him on his hind legs and be upright."

Animators turned to squirrel designs for inspiration for Rhino (right). Originally designed as a quadruped, the story demanded that he be a biped and act anthropomorphically. Rhino was then re-rigged using a new PSD.

So Rhino had to be re-rigged using a new PSD (pose shape deformer), and distance locators constantly needed to be adjusted. "There were too many in the neck, so we added locators in the arm," Kaytis adds. "Basically, we had to keep what he had and not throw away the rig, so it was a requirement on our part to figure out how to add everything to this rig so he could do two things within the same body. So we got together with the rigging TDs and they were very supportive. As animators, I made a small team and we explained the requirements, they went away for two days and came back with this solution of rigging. They actually experimented with it a little bit on previous characters, but nothing went into production with it. But they felt this rig that was a hybrid of a quadruped and a biped would shift between two different modes within a shot. For two months straight, we worked on it and in the end it was an awesome rig. It's the most complicated rig I've ever animated with. And it was kind of scary for animators to get their hands on it for the first time because sometimes it was like being in the cockpit of a 747. But the animators said it had everything it needed."

This was actually the first character that Kaytis has supervised and consequently his first rigging experience. "My solution had never been done before, but my riggers said it could be done and we ended up patenting the whole process of measuring the neck rotation. It was risky but very exciting. I stopped production on Rhino shots while he was being fixed, and that's where I say the leadership put a lot of trust in us. If it didn't work, it would've been a disaster on my part, but, luckily, it did work."

In terms of the overall visual style, the original plan for American Dog was to adopt a very painterly look in homage to Edward Hopper. As detailed in The Art of Bolt, this arguably posed the most complex challenge. Art Director Paul Felix continued working on Bolt with Look and Lighting Director Adolph Lusinsky. Although they maintained this painterly direction, they toned it down slightly in keeping with the more believable-looking character design.

Applying such a rigorous painterly approach to CG required lots of R&D on the part of the technology team (under the technical supervision Hank Driskill). As a result, Disney filed four patents on the R&D done in 2006 and 2007. These patents involved the massing/editing system, colloquially known as "look A/look B," which they fed into shaders so compositors could control depth, light and shadow; the normal painting techniques that make light play across a surface like painting (in which more detail was painted in modeling); the ray painting system in which a virtual object has painterly edges thanks to a series of cards with a transparent map (inspired by the matte work of Disney great Peter Ellenshaw); and the painterly shadow work.