Pause game play, then press Up(2), Right, Down, Left, Right(2), Circle, Square.
Legionnaire players
Press Down, Left, Down, Right, Down, Up, Square, Circle at the "Join Team" screen.
Master code
Press Up, Down, Up, Left, Down, Right, Up(2), Down, Left, Right, Left, Down(2), Up, Left(2), Right(2), Square(2), Left,
Down(2), Up, Circle at the credits screen to unlock all FMV sequences, teams, grounds, and special features.
Mech players
Press Left, Right(3), Down, Up, Down, Circle, Square at the "Join Team" screen.
Small heads
Pause game play, then press Circle(2), Down(2), Square(2), Up, Left, Down, Right.
Unlock City vs Country
Win the NRL Season (Any difficulty).
Unlock International Teams and Competitions
Win either the State of Origin or World Club Competition.