At the Title screen, hold L + R and enter the following cheats:
Play as Nicole:
Left, Up, Down, Up, B, Up, Up.
Play as Retro Harry:
Y, Left, Down, X, B, Y, Y, Left
Hyper punch mode:
Left, Right, B, Up, B, Right, Left.
Left, X, B, Down, X, A, X, B
B, B, Left, Right, B, X, A, Up, B. You can find it at the New Game screen.
Original Pitfall 2:
Left, Right, Left, Right, Y, Y, Y. You can find it at the New Game screen.
Global slow motion:
Y, A, Up, X, X, Up, B, X
Thanks to Revolution readers Brigitte, Harry and june!