'The Art of Toy Story 3'

“As an animator, you want to build up a certain depth of information that may never be fully explained in the film but will feed into what the audience sees. When the characters move a certain way, it just feels right. You don’t have to go into the depths of explanation, but someone has done the research, like an actor. We want to make the characters have a backstory, so they seem like they’re coming from someplace true, so they’re believable.” Bobby Podesta- Supervising Animator pg27/28