Extra Characters
At the 'Push Start button' screen, press Y, Right, Left, Y. A message will appear in the top right corner of the screen to confirm the cheat has been entered.
Extra Levels
At the 'Push Start Button' screen, press Y, Left, Right, Y. A message will appear in the top right corner of the screen to confirm the cheat has been entered. Select 'Puzzle Mode' and then 'Arcade Mode' to access the extra levels.