Inside Out isn't just a return to form for Pixar after several mediocre and/or half-baked movies (the empty sugar rush of Cars 2, the muddled Brave, the thematically rich but mostly derivative Monsters University). It isn't even just one of the studio's finest films. It's nothing less than one of the most complex, ambitious, and abstract movies that Hollywood has ever released with the hope that it will do blockbuster business. While Inside Out uses the general plot structure of mismatched individuals learning to trust each other during a journey -- a trope that's served the company well in Toy Story, Finding Nemo, and Up, among others -- that story line is given an entirely new spin when the setting is the mind of an 11-year-old girl and the characters are the personifications of her emotions. It's a buddy comedy that folds itself into a larger exploration of how our personalities are constantly fluctuating rather than set in stone, and how even mundane life events have an entire universe of psychological activity behind them. The 11-year-old in question is Riley (voice of Kaitlyn Dias), a seemingly ordinary American girl who loves hockey, her friends, her family, and acting like a goofball. Her life thus far has been relatively free of drama, which is why the control center in her brain is led by Joy (Amy Poehler). Joy was the first emotion to show up in Riley's mind when she was born, although she was quickly joined by Sadness (Phyllis Smith), followed by Anger (Lewis Black), Disgust (Mindy Kaling), and Fear (Bill Hader). The five of them collaborate to direct Riley's thought process, but Joy sees their main goal as making sure Riley creates as many happy memories as possible. That orderly process goes haywire when Riley and her family move from Minnesota to San Francisco due to her father's job. Try as she might to look on the bright side of things (mostly due to Joy's influence), she faces one disappointment after another: She finds her new home depressing and hates sleeping on the floor while they wait for the rest of their furniture, she cries when introducing herself to her new class, she feels her old friendships fading, and she loses her passion for hockey. The changes on the outside start affecting the inside, somehow giving Sadness more power. When Joy tries to regain control and put Sadness in her place, she causes an accident that ejects both of them from the center. Here's where the movie's ingenious structure reveals itself: Co-directors Pete Docter and Ronaldo del Carmen, aided by a terrific script by Docter, Josh Cooley, and Meg LeFauve, visualize Riley's thought process in ways that are complex enough to serve as a metaphor for how the competing aspects of our personalities guide our decisions, yet require a minimal amount of exposition and hand-holding to understand. With Joy and Sadness gone from the control center, Anger, Disgust, and Fear are in charge, forming the personality of your average sullen teenager (Riley's sarcastic new attitude comes from Disgust's failed attempts to act like Joy). Meanwhile, Joy and Sadness journey through the rest of her mind, from the halls of long-term memory to a decompression chamber labelled "Abstract Thought" to a movie studio where her dreams are produced. The various layers of the narrative impact each other in clever ways; in one particularly memorable sequence, Joy and Sadness crash a dream production in order to startle Fear (who's on slumber duty that night, watching the dreams on a screen in the control center) so he'll in turn wake up Riley. The story also makes room for an imaginary friend of Riley's named Bing Bong (Richard Kind), who turns out to be the film's most moving character -- he's been stuck wandering around the halls of her memory for ages, and while Joy promises him that he can return him to a place of a prominence if they work together, Bing Bong understands deep down that his days are numbered. The journey through the mind never runs out of fresh ideas or situations, yet it carries with it a level of thematic depth rarely seen in blockbusters or family-friendly animated films: Rather than making Sadness the villain, or even just the half of the buddy team who needs to learn to appreciate the other, Inside Out builds to a remarkably mature argument that growing up means accepting that most of your life isn't going to be joyful, and there's nothing wrong with that. How many mainstream movies aimed at adults are this emotionally honest? To be fair, the price of making abstract emotions the stars of the show is that Riley herself is a little bland. She has few distinguishing features aside from an interest in hockey, and the crisis she finds herself in (she's so homesick that she decides to take a bus back to Minnesota without her parents' knowledge) is low stakes on the surface. Riley is less a character than a setting, and much of the inside of her mind uses shorthand to get things across: Her biggest fear in her subconscious is a giant clown, she has dreams about her teeth falling out and coming to school without pants on, etc. These are experiences and neuroses that almost everyone in the audience can relate to, but it never really creates the sense that her mind reveals anything specific about her personality (it's also weird that the ending hints at the chaos that puberty will unleash in Riley in a few years' time -- wouldn't that stage of development have made for a more dramatic scenario for Inside Out, or is that being saved for the sequel?). Still, these aren't significant flaws so much as evidence that the movie's focus is elsewhere. This isn't a coming-of-age story about Riley, but a trippy adventure about accepting the ups and downs of life. That Pixar is able to take such an abstract, potentially complicated premise and turn it into a film that's equal parts funny, thrilling, and bittersweet is proof that, at their very best, there's no one working in mainstream pop culture today who can match them.