Here are a few of the ideas I might be using.  If you have any ideas, feel free to submit them!

• There are going to be 3 or 4 "secret" characters.  Certain events in the game will require that you win/lose a battle or make a certain choice, and if you do, you get that character and that character only.  You can't get any of the others.
• A dating minigame.  (You get to choose to play as either of the two main characters beforehand.)  The more pleasant the date, the better the item you get afterwards.
• Several different endings.  I have an idea for one that basically compromises the entire storyline...
• Cameo appearances of some other "characters," and possibly even references to the real people who inspired some of the minor characters.

If you have any sort of ideas for this game, feel free to post and tell me!