S=Square
T=Triangle
O=Circle
X=X

Start a game, pause it (use the START button), select options, and enter a 
code. You will hear a "click." Exit theoptions menu Press S. You will get a 
secret options menu. Greyed-out choices require another code. Use 
Left/Right on control pad to change settings.

Invisible Walls - XXXTSSST - no more out of bounds
Curve Ball - TSXTXX 
Super Power - TSTTTTTTTT 
Super Goalie - SSSSSTTTTT 
Super Offense - SSSSSTX 
Super Defense - TTTTTXT 
Shootout - STSXST - go straight to shootout 
Stupid Team - STXSTX

After entering the following codes (using the same method to enter the 
above codes), go back to the Main Menu (you must quit your game) and 
select OPTIONS to see new choices found at the bottom.
Formal - STXSTTXT - tuxedoes as uniforms
Federation - STXSTTXX - Data and Spock
Dynamic Duo - STXSTTTS - Batman and Robin (from t.v.)
Default Color Pallete - STXSTTTX - ?
Invisible - STXSTTXS - just hair, shorts, shoes

EA Custom Teams:
Enter the code STXSTTS in the option and you can use 5 teams united by 
EA staffs with dream ability.

Go into the options screen and enter sstsxxo. Now go back to the options 
screen and hold triangle for tenseconds now go into the game and one of the 
teams should be wearing red boots, blue outfits, and a red cape.