At the main menu, hold all four shoulder buttons to bring up the cheat menu. Then enter one of the codes below to activate the corresponding cheat:

Big Head Mode: SQUARE, CIRCLE, CIRCLE, X, TRIANGLE, X, SQUARE, CIRCLE
Secret Teams: X, TRIANGLE, X, SQUARE, CIRCLE, SQUARE, X, TRIANGLE
The Difference Stadium: SQUARE, CIRCLE, SQUARE, TRIANGLE, TRIANGLE, CIRCLE, X, X
Win Match: X, TRIANGLE, CIRCLE, X, SQUARE, CIRCLE, TRIANGLE (Pause the game to win it)
View Credits: CIRCLE, SQUARE, TRIANGLE, CIRCLE, X, TRIANGLE, TRIANGLE, SQUARE