Inside Out concludes with a callback to the very beginning of the film. Allow us to refresh your memory.
The movie starts with Joy setting the scene, via voiceover. We meet the rest of Riley's emotions, learn what Core Memories and Personality Islands are, and see that everything's great in Riley's world. She has rad friends, loving parents, and a cozy house. Oh, and she's moving to San Francisco—which jump-starts the film's narrative.
At the end of the flick, we get another status update from Joy, as we watch Riley play hockey. It's been a rough year, but everything's copacetic again: Riley's got awesome friends, loving (if not slightly embarrassing) parents, and a nice house. Joy tells us that's Riley's 12; what could go wrong?
The joke here, of course, is that just about everything could go wrong, since Riley's about to become—gasp—a teenager.