Enable Classic Asteroids:
At the title screen, hold Select and press Circle, Circle, Circle, Triangle, Square, Square, Circle. You will hear a sound to confirm correct entry.
Classic Asteroids Game Codes:
Extra Life - Up, Down, Left, Right, Circle, Square, X, Triangle
99 Lives - Up, X, Down, Triangle, Left, Square, Right, Circle
Invincibility - Down, Down, Up, Up, Circle, Square, Triangle, Triangle
Unlock Excalibur:
At the title screen, hold Select and press Triangle, Circle, Circle, Triangle, Square, Circle, Square. You will hear a sound to confirm correct entry. You can alternatively just beat the game on Expert or Hardcore.
Level Select:
At the title screen, hold Select and press Square, Triangle, Circle, Triangle, Triangle, Square, Circle. Now start the game, then hold SELECT and press START to access a secret menu that allows you to select any stage or turn the "Collision" off to become invincible. Once you've picked a starting stage, press L1 to warp there.
GameShark Codes
Infinite Lives 8011013c0009