Enter your name as LINES for a hidden game.
To play some hidden tunes, enter your name as "G(alien head)MEBOY".
To view the credits, enter your name as CREDITS.
To access any level, enter your name as "(saturn)(spaceship)(rocket)(heart)(skull)".
At the "NEW NAME" screen press L, C-Right, C-Down to bring up the secret characters.
At the "NEW NAME" screen enter your name as VORTEX, then press and hold the RESET button.