In my view, the Mentor is Dug, voiced by the movie’s screenwriter Bob Peterson. This may cause some head-scratching, but consider this. First, Dug is the character who has the most insight and understanding of the jungle, Muntz, and Muntz’s other dogs — and with this ‘wisdom’ fulfills at least one function of the Mentor character. Also Dug plays a pivotal role in assisting Carl in the Final Struggle, another role often played by the Mentor. But I think the most important mentoring Dug does is by providing a symbolic conduit for Carl to see Russell with ‘new’ eyes. For just as Dug is loyal, trustworthy, and dogged in his pursuit of that which is good, so is Russell. Indeed, the identification — as far as Carl is concerned — between Dug and Russell is such that they share an exact same beat: The house rises into the air, Carl settles into a chair, then a knock at the door. First time, it’s Russell; later, it’s Dug.