Super Kick
When you have control of the ball, press B and then A really fast. The ball will change to a purple color, and anything in its way will be knocked down, including the goalie.
Useless Enemies
At the straregy screen before the start of the game, you can choose to tackle or mark the enemies. Choose tackle and during the game, keep knocking down the same enemy or kick the ball at them hard. Eventually after about 3 or 4 hits, the enemy will lay on the field, unable to play.
Level Warps
At the main screen where you can enter a password, type in these codes one at a time:
Skip To 2nd Round: 10300
Skip To 3rd Round: 30700
Skip To 4th Round: 01500
Skip To 5th Round: 22000