In the attract mode for the arcade version, there is a one second clip of Rain fighting Shao Kahn, despite the fact that Rain does not appear in this version. This could either mean that Rain was meant to be added to the game or that he was placed there to make fans speculate on if he's real or not.
By using a Game Genie on the Genesis, the player can use Chameleon. He is clearly unfinished as he has no combos, special moves, or fatalities, uses Scorpion's sprites (with the sprite changing to Rain's when a decapitation fatality was performed on him), and the announcer does not say his name. This hints that he was planned to be put in the game before he was debuted in Mortal Kombat Trilogy.