During early stages of the game's development, Axel Stone and Adam Hunter had different names. Axel's name being Hawk and Adam's name being Wolf.
In a two player game, at the final boss, Spoiler:if one player answers yes and the other answers no when Mr. X says "Well, you found your way here. Would you consider becoming my right-hand man?", the two players will fight against each other. This is the only way to access the "bad" ending, in which the player takes over the syndicate.