I just rewatched Inside Out again last night so this thread is timely. I'd forgotten how good it is to be honest. Seriously. Funny and sad and just great overall. As for a sequel there's lots of possibilities but how to do one so it not only builds on the original but also works as a standalone film. One key thing about the original is that there were only 5 emotions so it was manageable, and I think that worked for child Riley but not for adults. Do Riley's parents really only have 5 basic emotions? One of the great things about the original was the lesson that core memories can be mixed emotions - the whole movie all memories are only one emotion but at the end we see sadness and joy in the same core memory. Maybe they could build on that idea - how the 5 basic emotions can combine to form more complex emotional states. They should avoid the obvious - just making another one that picks up where the original left off.