Pause the game and then press and hold the L and R buttons at the same time. Then press B, A, B, A.
Pause the game and then enter these codes:
While the game is paused, press Left and Y together for a clear view of the matrix effect
While playing as Doctor Hawkins, press [L], [R], [Left] and [A].
While playing game press pause and press X+Y simultaneously to get a clean game screen without text