This is definitely interesting. Did you know that Dissidia: Final Fantasy was originally intended to be developed for the PlayStation 2 and not the PSP? Why the change in platforms?
According to Gamekyo, Tetsuya Nomura has revealed that the PSP simply offered more options in order for them to integrate more into the game. For example, if it weren't done on the PSP, the trading system or the duels via wi-fi wouldn't have been possible in-game.
Another interesting trivia: Dissidia was originally supposed to be named as "Shade Theory: Fina Fantasy."