Inside Out, the 15th animated feature film from Pixar Animation Studios, opened this weekend with an estimated $91.1 million in North America, rocketing past Avatar's $77 million opening to become the best debut for an original movie in Hollywood history. (It is also the best debut gross for a film that did not open at number one. Jurassic World continued its astronomic box office run with an estimated $102 million in its second weekend.)

Inside Out is something of a combination of all the best parts of Toy Story, Monster's Inc. and Up. It's a story of friendship and loss, of a young girl and her parents dealing with a hard move to a new town, and the loss of innocence and that care-free joy that comes with a happy childhood as it's dashed upon the rocks of adolescence.

The central players of Inside Out, are emotions-Joy, Fear, Sadness, Anger, and Disgust-inhabiting a young girl's mind and brought to life by a murderer's row of voice talent like Amy Poehler and Bill Hader. But while casting was a breeze, picking the emotions wasn't. (Schadenfreude was an early contender.) Turns out there's no consensus on how many emotions there actually are-so director Pete Docter and his team turned to an expert they'd worked with before.

Early in the movie's five-year production, Docter invited psychologist Paul Ekman to brief the crew on the nature of emotions. According to Ekman, who has had a long and sometimes controversial career, there are seven emotions with universal facial signals-those that ended up in the movie, plus contempt and surprise. For story purposes, Docter needed simplicity; five, he says, was "just enough for dissension and entertainment." Ekman applauds the movie for teaching kids and parents alike about emotion-that understanding, he says, allows us to "choose what we feel, rather than being controlled by our emotions." Then again, if we could choose what we feel, we wouldn't cry so much during Pixar movies.