http://www.polygon.c...acter-selection
I don't know if this is on here yet, (I apologize if it is), but Polygon interviewed Sakurai, and adding / removing characters is driving him insane, because he doesn't want to make anyone unhappy by removing characters people love, but he wants to add new ones. I thought it was pretty interesting. He also talks about the balance of the game, mechanics of certain characters, and so on.
An interesting read!