Metal Morph

Cheat mode:
Press Start to pause game play, then press Up, Down, Left, Right, X, B, Y, A. Resume the game to have invincibility. Hold A and press the D-pad to activate free movement in the current level. Press Select to skip the current level.

Weasel mode:
Press Start to pause game play, then press L, R, L, R, A, B, A, B, X, Y, X, Y. The "Level Select" option will now be unlocked at the options menu.