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At the end of the game, Princess Prin Prin's shot in the credits roll call displays three sets of numbers and letters below her name. These are her bust, waist, and hip measurements in centimeters. This is most likely a direct reference to Street Fighter II: The World Warrior, another Capcom game released earlier the same year in 1991, where the new fighter Chun-Li shares these exact same measurements.
Contributed by MehDeletingLater
Sardius, the final boss, was named Samael in The Japanese version. In Hebrew, Samael means "venom of God" or "poison of God". In Jewish lore, Samael is the archangel of death. The name change may be due to Nintendo's anti-religious reference policy.
Contributed by Kakariko Kid
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The crosses in the first level of the game were changed to ankhs outside of Japan.
Contributed by ProtoSnake