The drive of the story is sort of hinted at the beginning, is Joy and Sadness and those two characters. Especially Joy starting to understand that there's more to life than being happy. And so that's based on real life observations and things that we've learned as adults.

You have to think about good storytelling and characters first. Then hopefully, the rest of that stuff will follow, some more than others. But if you don't have a good film and strong characters, then you don't have anything down the road.

And it's about a three-month process every screening. And that way we have seven or eight chances at the film before we have to actually build the models, build the sets, do the animation and all of that. So it's a - I think that's a real key to the way we make films.

Dr. Paul Ekman, who worked in San Francisco - still does - which is where Pixar Animation Studios is, he had early in his career identified six. That felt like a nice, manageable number of guys to design and write for. It was anger, fear, sadness, disgust, joy and surprise.

My father was working on his Ph.D. on Danish choral music - the Danish choral music of Carl Nielsen - so over there to do research.

And as I was sort of doodling, I was thinking, surprise and fear - probably fairly similar so let's just lose surprise. And that left us with five.

People are funny -- they are able to project personality onto anything. I remember as a kid I spent a $ 5 bill once and felt so bad because the other $ 5 bill was now going to be lonely without all the other bills I had in my wallet, you just invest these dead things with life and that is our tendency as people. So animation takes advantage of that, grabs on to it, and runs with it.