Cheat mode:
Press Turbo (default is Z), Jump (default is B), and Pass (default is A) to change the icons below the helmets on the versus screen. The numbers in the following list indicate the number of times each button is pressed. After the icons have been changed, press the D-pad or Analog-stick in the indicated direction to enable the code. The name of the code and a sound will confirm correct code entry. Example, to enter 1-2-3 Left, press Turbo, Jump(2), Pass(3), Left:

Team tiny players 3-1-0 Right
Team big players 1-4-1 Right
Team big heads 2-0-3 Right
Power-up teammates 2-3-3 Up
Power-up blockers 3-1-2 Left
Super blitzing 0-4-5 Up
Headless team 1-2-3 Right
Roman stadium 5-0-3 Left
Snow field 3-0-4 Up
Fog on 0-3-0 Down
Infinite turbo 5-1-4 Up
Future stadium 5-0-2 Left
Super field goals 1-2-3 Left
No interceptions 3-4-4 Up
No random fumbles 4-2-3 Down
No first downs 2-1-0 Up
No punting 1-5-1 Up
No head 3-2-1 Left
Snow stadium 5-0-3 Down
Thick fog on 0-4-1 Down
Weather: clear 2-1-1 Left
Power-up offense 3-1-2 Up
Power-up defense 4-2-1 Up
Big head 2-0-0 Right
Huge head 0-4-0 Up
Night stadium 5-0-2 Down
Grass field 3-0-0 Up
Dirt field 3-0-2 Up
Astroturf field 3-0-3 Up
Fast turbo running 0-3-2 Left
Fast passes 2-5-0 Left
Turn off stadium 5-0-0 Left
Late hits 0-1-0 Up
Show field goal % 0-0-1 Down
Old day stadium 5-0-1 Up
Day stadium 5-0-1 Down
City stadium 5-0-1 Left
Old night stadium 5-0-2 Up
Asphalt field 3-0-1 Up
Show punt hang meter 0-0-1 Right
Use team plays 1-0-0 Up
Hide receiver name 1-0-2 Right
Invisible receiver highlight 3-3-3 Left
Old snow stadium 5-0-3 Up
Weather: snow 5-2-5 Down
Weather: rain 5-5-5 Right
Invisible 4-3-3 Up
Big football 0-5-0 Right
Green Bay Packers playbook 1-2-2 Left
Allow stepping out of bounds 2-1-1 Left
Night game 0-2-2 Right