Level Select
Press X(4), B(4), Y(4), X, B, Y at the main menu.
A message will confirm correct code entry


All boarders:
Rotate the Right Analog-stick clockwise fifteen times. 
A message will confirm correct code entry.


Second and third boards:
Press Up(2), Left(2), Right(2), Down(2), Up, Left, Right, Down, Up, Left, Right, 
Down at the main menu. A message will confirm correct code entry.


Completion bonuses:
Successfully complete all levels to unlock the credits stage, a video of your 
character, and Summer, the first hidden character