Space Invaders Codes -

Nine lives:
Pause game play and press Right(3), Down, Circle, Left, Down.

Five shots:
Pause game play and press Down, Left, Circle, Down, Right(3).

Level select:
At the main menu, select either one or two players and press Circle (instead of X) to begin the game. A selection screen that allows any level, including planet Mercury with a new power up and an "Alien World" featuring the best background in the game.

Classic mode and credits:
Enable the "Level select" code, choose level 00, and complete it to unlock an ending, classic mode, and credits. Press Right when selecting then number of players to access classic mode. Enter the options screen to access the credits.