Enter JEHUTY as a password to get a card featuring Jehuty from Zone Of The Enders. This card will destroy all equipment and equipment level-ups in the current room.
Enter KAREN as a password to get a card featuring Karen from Policenauts.
Enter MIKA as a password to get a card featuring Mika from Snatcher.
Enter VIPER as a password to get a card featuring Black Arts Viper from the Metal Gear Solid on the Game Boy Color.
Enter XMEIGHT as a password to get a weapon card with 50 attack, 60% hit, 5.56mm bullets, 6 shots, 70% reaction, move 6 spaces, knockback, and burn.
Bikini model clip
Enter SABRAGE, NOMEL, ELYTS or MAEB as a password to see clips featuring Japanese bikini models. These will cause Snake to get a nosebleed, but has no effect on Teliko. Note: This feature is only available in the Japanese version of the game.
Link battle option
Successfully complete Stage 06 to unlock the "Link Battle" selection at the "Options" menu under the "Intermission" screen.