Yesterday I went to see Kung Fu Panda 2 and was surprised at how good it was.
Normally sequels are a dicey proposition. Sometimes the writers don't understand exactly why the first movie did so well, so when they create a sequel they try to just redo the first movie, only slightly different. They replay the same gags, and the characters never seem to know what they are doing.
Happily, this did not happen in Kung Fu Panda 2. They took the characters you saw in the last movie, and expanded on them. Po is now the Dragon Warrior, and fighting together with the Furious Five to protect the Valley of Peace from bandits.
The villain comes in the form of a peacock, Lord Shen, who is not playing with a full deck. He plans to rule China not with Kung Fu, but with a powerful new weapon using gunpowder. If that sounds awesome, that's because it is.
In addition to an interesting new villain, we get an amazing origin story for Po. I can't really say more than that without giving away part of the movie, but Po and Lord Shen have some history together that instead of revealing right away, the writers instead chose to drag it out for a satisfying conclusion, since we the viewer know the answers that Po is seeking from Lord Shen.
The writing is good, they develop Po in a satisfying character arc, and once again, the music is simply beautiful. Somehow they balance all of that with Po screwing things up and laughing while he's doing it. Instead of making him seem like an idiot, to me it just makes him more human. Or more panda if you prefer.
There were several scenes in the later part of the movie, where Po is working through his personal demons to reach inner peace that had me tearing up. I can't remember the last time I saw such a poignant scene where the character searches inside themselves, through a haze of misery and pain, to find what they are truly made of.
In short, if you want to write a great sequel, be it book or a movie, you have to maintain the character you developed in the first part, but continue to develop him in new and interesting ways. You want to bring the viewer/reader back to the world they loved in the first part, without acting like nothing has changed and you're just going to repeat what happened previously. This cheapens the first part, because then it feels like the first movie or book was for nothing and now you're sitting through more events that have no impact on the character. Instead, find new ways that you can test your character.
You're all creative. I am sure you can come up with something.
What about you? What makes a great sequel for you?