Start a regular game and pause it. Then press Right, Down, Left, Up, Right, Down. Unpause the game, and the referee will be a giant.
Clear Codes
To disable any codes you've entered, pause the game and press A, X.
Large Players
Pause the game and press R, A, P.
Resize The Players
Pause the game and press B, A, B, A, X, B, A, X. Unpause the game, and the players will return to normal size.
See Computer's Play
Pause the game and press B, L, A, B.
Shrink The Players
Pause the game and press the Stop (X) button five times. Unpause the game, and the players will be smaller, which makes it harder for the opposing team to tackle your players.
The Incredible Shrinking Referee
Pause the game and press Left, Down, Right, Up, Left, Down, Right. Unpause the game, and the referee will be pint sized.