Hold L + R and enter the following:
Bottomless canteen: LEFT, B, X, DOWN, B, A, B, X
Original Pitfall: X, X, LEFT, RIGHT, X, B, A, UP, X
Hyper Punch Mode: LEFT, RIGHT, X, UP, X, RIGHT, LEFT
Play as Nicole: LEFT, UP, DOWN, UP, X, UP, UP
Pitfall II
Collect and use all Idols.
Unlock Pitfall 2: The Lost Caverns
On the title screen, hold L1 and R1, then press Left, Right, Left, Right, Y, Y, Y.