This is cool if you just want to fight all the time, because, in fact, you'll be fighting every second with this code on. Good to surprise a friend, maybe. During a game, go to the Options menu and highlight fighting. Then hold L (left) and press these C buttons in this order: RLLRBTTBLRRLRL. R=right, L=left, B=bottom, T=top. If you've entered it correctly, a string of zeroes will appear on the bottom of the screen.