Invincibility:
Press Start to pause game play, then press Left, Right, Left, Right, Up(2), Down(2), Left, Right, Left, Right, Up.

Alternately, press Start to pause game play, then press Up(2), Down(2), Left, Right, Left, Right.

Super speed:
Press Start to pause game play, then press Left(3), Right(3), Up, Down.

Alternately, press Start to pause game play, then press Right(3), Left(3), Up, Down.

Super jump:
Press Start to pause game play, then press L, R, L, R, Up(3), Down(2).

Remove graphics:
Press Start to pause game play, then press Up, Down, Up, Down, Up, Down, L, R.

Hard difficulty:
Successfully complete the game, then start another game with the cleared save file.

Level select:
Collect all sixteen Bat symbols when playing under the hard difficulty setting.