The lack of villain was one of my favorite bits. There isn't a big twist, there isn't a plot to save a world, or some life-ending destruction that must be stopped. And yet, the stakes have never felt so important. This is a story where a little girl's very psychological existence is at risk, and because it's such a personal story, it feels all the more real. Riley's situation is endlessly relatable, as it deals less with specific scenarios (though it may certainly help if you've ever moved away from a place you call home), and more with emotional turmoil at a very trying age that everyone can connect to. And because of this, it's why Inside Out feels important, not just to those have undergone hard times in their life at one point, but those who are currently undergoing such difficulties. This film, for all the childlike wonder it possesses, is very mature.
Nearly every bit in the Memory Dump is designed to make you cry, by the way. Lot of onions must've been in the theater during these scenes.