Knightmare II: The Maze of Galious

If you insert another Konami game cartridge in slot B you can get some interesting effects.

Q-Bert in slot B.You start with full vitality and 100 Arrows, Coins and Keys. Knightmare in slot B. You can revive Popolon or Aphrodite 99 times in death's shrine. Normally this can be done only once, but if you ask the password of the game and re-enter it, you can always do it again.