When two players select Sub-Zero in versus mode, his player 2 outfit is recolored black, resembling Noob Saibot.
At one point in development Mortal Kombat: Shaolin Monks was intended to be a single player game featuring Raiden as the only playable character.
A hidden survival mode can be found in the foundry stage. It was apparently never finished, and was removed from the main menu. However, it can still be accessed in-game through a long and complicated procedure.