The Princess Merida’s hair was almost a three year process to get correct. Earlier hair such as for the characters in The Incredibles had much more groomed hair, but here the character’s hair simulation needed to solve how to get this messy, tempestuous and unpredictable look while still looking attractive and flowing nicely with the animation.
It’s the details.
There’s a lot of talent and brainpower at Pixar. I have a friend who’s worked there for a while and she said that the current requirements for a PA (the person who gets her coffee) are a Bachelor’s degree and experience in film.