Unlock Dungeon Mission
During Mission 5 the dungeon card. Once you complete mission 5, go to the mission select screen and to the top left there should be an extra mission called dungeon.
Unlock Boss Cards
During with foght with a boss, you have to take him out quickly to get its card. Grenades, the Metal Slug and special weapons are good for this. A message will appear on screen letting you know that you have the card.
