Anger is about fairness. If it feels that you're getting ripped off or taken advantage of, that's when anger comes up. Sadness deals with loss. And I suddenly had this new revelation - it felt like to me - that those are all true, but the real, deeper reason we have emotions is to connect us together. And that felt big to me.

It might have been introduced slowly over the course of the years as you recall this memory over and over. So that was a very cool but complex idea that we thought about representing in the film but could not find a way to make it work.

Yeah, we were looking for a way to represent adulthood and the passing into adulthood. And I think, for me personally and a lot of the folks that I work with, childhood is kind of a sacred, special kind of point in time that has a real joy and purity to it. And we sort of long on a daily basis to reach back and kind of grab onto that in some way.

It is one of those weird social things. Even as parents we say, oh, don't be sad. You know, come here, we'll distract you with some ice cream or something. And I don't know if that's always the best thing. But it's certainly - you understand why people do it.

Any great movie you watch has some element of darkness or loss or some suffering in it. That's what makes the fun parts fun.

Well, we try to - we definitely try to have a balance. And I think things have gotten a lot better at Pixar. When we did "Toy Story," that was an all hands on deck situation that really was time intensive.

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.