Mark Walton initially worked as a screen story author in Disney Studios' animation department, specializing in visual development and character development on CG-animated features, including Tarzan (1999) and The Emperor's New Groove (2000). He soon found a much different and more publicly visible niche for himself, however, when Disney personnel employed the occasional practice of pulling coworkers in to do preliminary test voices on animated features.
Walton was one of those tapped, and his efforts generated so much popularity among the producers that he evolved into a veritable mainstay of animated voice-over work, voicing characters on studio features including Home on the Range (2004), Chicken Little (2005), and Bolt (2008). ~ Nathan Southern, All Movie Guide. 