I know John Lasseter mentioned somewhere that getting the basics right in drawing is the first and foremost thing to get right, which I imagine you’d need formal education for to an extent. Having said that, I don’t know much on the subject, but I imagine that they look for talent and potential more than they do qualifications.
This is possibly true, but I don’t know. Now, Pixar is not entirely made up of animators, so if someone’s applying for a job outside animation, simply having a strong background in drawing, color theory, design, storytelling, and so forth may be enough. Animation is such a complex medium that people might be better off finding a school that teaches it. However, there are so many animation resources out there now! Countless books, videos, animation programs (Blender), etc. I don’t know about Animation Mentor, though, because it’s so expensive from what I remember. I wish I could attend Cal Arts but I couldn’t possibly afford it and being accepted would be difficult enough.
I’ve heard that a graduate from my school’s art department, which doesn’t teach animation except for a basic course in non-traditional animation techniques, has worked at Pixar.
There are certainly people without a degree, or with a degree totally unrelated to what they do professionally, working at Pixar. Non-degree granting programs like animation mentor send a significant number of people to Pixar, as well as people who self-taught and/or learned at other studios.