While you are at the title screen, press R1(4), R2(6). If the code was entered in correctly, you will hear a sound. Then, a "Sound Test" option will appear on the "Mode Select" screen.

Extra Ark

Enter "Astarte" as a name for an extra 2800 Ark.

Evil Upper and Evil Stomp

Beat the game and get the first ending to get the Evil Upper and Evil Stomp. To get the first ending, kill everyone in Chapter 17 and Chapter 21 (Two Wrongs Equal One Right).

Magic Sac

Beat the game and get the second ending to get the Magic Sac. To get the second ending, let at least one person escape in Chapter 17, and kill Keith in Chapter 24 (Shared Wounds). The Magic Sac does not do any damage, but it immobilizes an enemy, allowing you to push them anywhere.

Ardebaran Mask

Beat the game and get the third ending to get the Ardebaran Mask. To get the third ending, let at least one person escape in Chapter 17, and let Keith live Chapter 24 (slightly damage him). The Ardebaran Mask does a lot of damage, and it makes the victim walk straight.

Evil Kick

Beat the game and get the fourth ending to get the Evil Kick. To get the fourth ending, kill everyone in Chapter 17, and let at least one person escape in Chapter 21. The Evil Kick is a very powerful trap that sends a victim flying across the room.

Suezo

Get all four endings and save them to a memory card to get the one-eyed yellow monster from Monster Rancher, Suezo. The Suezo has no animation, but is a very powerful trap.