It's a little bit difficult to decide whether the emotion lies in the movie or in the memories it evokes. I'd imagine it's a completely different experience for a child viewer, a teenager, or a parent, but I suspect the last two appreciate its full weight far more than young children would. It's not that kids won't like the film: to the contrary, it feels like it's designed for younger viewers, unlike Ratatouille or The Incredibles (my two favorite Pixar films.) It's merely that this story is more about the loss of childhood than the celebration of it. This bittersweet feel is similar to that in Toy Story 3.
These memories are fashioned by her five emotions: Joy (an enthusiastic Amy Poehler), Sadness (Phyllis Smith), Disgust (Mindy Kaling), Fear (Bill Hader), and Anger (Lewis Black.) Up until this point, Joy has had complete control, but glimpses into the minds of Riley's parents - where Sadness and Anger are the primary fueling emotions - foreshadow that things may be about to change. Joy recognizes the place of Fear, Disgust, and Anger - they keep Riley safe. But Sadness, that most adult of emotions, seems to have no function whatsoever. In a more typical movie, Sadness would have been cast as the villain. But this isn't a typical movie.
Once Riley arrives in San Francisco, all of her happiness comes into question. We follow her through the events of the move, her first day at school and trying out for the hockey team. Inside of her head, something has gone terribly wrong, and the emotions have to work double time to get things right. It's clever how the movie uses the emotions - you can almost fool yourself into thinking that what happens to Riley is a consequence of what they do, but in the end, you know that they are an allegory for her mind, not the other way around. But the emotions don't know what the viewer knows must happen: they expect childhood to continue forever, and memories to remain simply happy or sad or angry or fearful or disgusting.
The rest of the movie takes place over the space of a few days, as Riley's emotional life crumbles and she has to redefine herself. Looking back, the whole thing is not all that huge a crisis, but it's magnified by the drama of her anthropomorphized emotions. It reminds me of Lord of the Flies (bear with me) in that the film does a great job of getting us into a child's head. It's surprising to look back and, like returning to a childhood home as an adult, realize how small everything was, after all.
Childhood is a complicated thing. We see Riley's happiness, but also her immaturity. In the end - and here's kind of a spoiler - the resolution comes through growing up, not embracing childhood. Sadness can lead us just as sensibly as Joy, and perhaps even the other emotions - in their proper place - have a role in engaging the world wisely. Being happy isn't the most important thing.
I'm not as impressed with the film as some. It's good, but not amazing. I wasn't a huge fan of the over-colorful milieu it embraces in its Inside sequences - it felt too much like other bright children's films I've seen, and lessened the impact of the dark Outside. I didn't find the idea as original as other did, either (I'll admit, I was thinking of Osmosis Jones, a film which is probably really terrible, but the last time I saw it I was six.)
There was too much of a focus on preschool imagery for an eleven-year-old - by that age I was obsessed with dragons and pirates, rather than clowns and pink elephants. Because one could see the direction of the allegory, the story could be predictable, and I could foretell events some time before they actually happened.
On the other hand, Inside Out has tons of strengths. It's the most original Pixar film since Up, and Riley's family is the best Pixar family since The Incredibles. The emotions are terrifically voiced and animated - my personal favorite is Phyllis Smith's sullen, melodramatic Sadness, but Poehler is wonderful as ebullient Joy. They're Pixar's first female duo - follow-ups to Mike and Sully and Buzz and Woody.
The filmmakers have a ton of fun with Riley's mind - I especially loved the dream sets, sub-conscious, and Imaginary Boyfriend. It's really very funny - at moments, I defied the silent theater to guffaw uproariously at subtle jokes. (Or the not-subtle ones: "GIRL - GIRL - GIRL.")
Ultimately, I think the biggest compliment I can give to the movie is that (no pun intended) it got inside my head. I'm still young enough to vividly remember the confused emotions and insecurity of adolescence. These days, I often have opportunities to reflect on what my sixteen-year-old self would make of the things I'm doing now. Watching old family videos with horror just last week, I realized I have almost nothing in common with eleven-year-old Hannah. And what a complete idiot she was. And how happy she was in her idiocy! Dangit, Pixar. Inside Out is going to keep me thinking about those things for some time to come.