Classic Asteroids:
On the "Press Start" screen, hold down the Select button, and (while holding it
down) press circle, circle, circle, triangle, square, square, circle. You'll hear a slight asteroid
explosion sound. When you press Start, there will
be an extra option on the Main Menu screen.... Classic Asteriods.

Submission:
Khabal [Khabal@l33tz.org]

Excalibur ship:
Hold Select and press Triangle, Circle(2), Triangle, Square, Circle, Square when "Press Start"
flashes at the title screen. The sound of an exploding asteroid will confirm correct code entry.

Level select:
Hold Select and press Square, Triangle, Circle, Triangle(2), Square, Circle when "Press Start"
flashes at the title screen. The sound of an exploding asteroid will confirm correct code entry.
Then, press Select + Start during game play. Use the D-pad to select a new level and zone, as well
as toggle collision detection. Press L1 to resume game play.

Extra life (Original Asteroids mini-game):
Press Start to pause game play, then press Up, Down, Left, Right, Circle, Square, X, Triangle.

99 lives (Original Asteroids mini-game):
Press Start to pause game play, then press Up, X, Down, Triangle, Left, Square, Right, Circle.

Invincibility (Original Asteroids mini-game):
Press Start to pause game play, then press Down(2), Up(2), Circle, Square, Triangle(2).

Armageddon Alternate:
Hold Fire for approximately five seconds for an Armageddon without collecting the corresponding
power-up.