Hold Up and press 2 eight times at the game over screen. Note: This code may only be enabled if there is a total of $400 or more when game play ends.
Go to the second question mark in the first level. Punch it out and a ghost will appear. Run away from it. Go to the question mark at the end of the level. Punch it and there will no longer be a ghost where one usually appears. Instead, an extra life will appear.