You might try "Final Fantasy The Spirits Within" as a second or perhaps as the long animation prelude to Serenity. I watched the Firefly series when it was on TV and really liked it, but haven't seen Serenity yet.
I think Final Fantasy was another of those quirky, twisted Sci-Fi movies and a landmark animation film. However, my wife played through all of the Final Fantasy games, and we have some grasp of Japanese culture to help interpret what can be an occasionally confusing movie so perhaps it's not for everyone. I'm anxiously awaiting the release of "Final Fantasy VII Advent Children" here in the USA. I saw the Japanese version and thought it was pretty good, but it required some narrative from my wife who played the game.
