Choose Opposing Team
Before you choose your team, hold down B and push right. Your selection should switch sides. Now you can choose the team you play against and their line up (don't push A or you'll be them). After you choose the team, hold B and push LEFT and now you may choose your team.
Highlight FIGHTING on the Options screen, then hold L and press C-Right, C-Left, C-Left, C-Right, C-Down, C-Up, C-Up, C-Down, C-Left, C-Right, C-Right, C-Left, C-Right, C-Left. A line of numbers will appear at the bottom of the screen if the code was entered correctly. This code has to be entered every period and will cause a fight to break out almost every time you check someone.
To create an invisible team, perform the following.
At the Options screen, hold C-down and press R to access a new menu. To use it, enter one of the codes below.