Level 22 (Start):
Submit the password 2R3KD4RG0J9D3YT0664LJ.

Level 22 (final Boss):
Submit the password YNzYSMChriGIgLV-ihOdfCGe.

Invincible player two:
Submit the password any valid password for player one, then enter KKKKKKKKKKKKKKKKKKKKKKKK for player two.

Level 45 character:
Start a new game in one or two player mode and select a dungeon. Immediately press Run when game play begins to display the current password. Replace characters 10 through 14 in a one player password with "NNNb". For a two player password, replace characters 34 through 38 with the same sequence. Reset the game and entered the modified password to begin game play.

65535 HP:
Submit the password Player01 or Player02, with the remaining password locations filled with + or - characters.

Hint: Pass up enemies:
If you reach an enemy that you can not defeat, turn rapidly back and forth while pressing Attack and holding Forward. If done correctly, you will walk right over the enemy.