You must enter these codes at the Title Screen.
| Code | Effect |
| B, Right, A, Down, Right, Up, B, Left, A, Up, Right, A | Allows you to choose which level to start on. Use Up and Down to select.
| | Down, A(x26) Down | Atari Pitfall
| | C, Right, Down, C, Right, Down, C, Right, Down | Displays the credits
| | B, A, Right, C, Right, Up, Down | Gives Harry super speed.
| | C, C, C, C, Left, A, Down, Up, Down | Gives Harry unlimited continues
| | Left, A, Down, B, Right, A, B, Up, Down, A, B, Up, C, A, C, A | Gives you extra weapons and lives at the beginning of the game.
| | Right, A, Down, B, Right, A, B, Up, Down | Grants Harry 9 lives.
| | A, B, Up, C, A, C, A | Grants you all weapons at the beginning of the game.
| | B, A, Down, C, Right, A, B | Lets Harry practice the lever game.
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