Romance on the Set: Ho-sung Pak (Liu Kang) and Katalin Zamiar (Kitana) dated while working on the game together and is part of the reason why their characters became lovers in later games and movies (ironically where they were played by other actors).
There were plans to have a character with hooked swords for Mortal Kombat II. Due to hardware limitations, he was modified to become Baraka. The design was modified again to become Kabal for Mortal Kombat 3.
Kintaro was originally going to be an anthropomorphic tiger, and a playable character in Mortal Kombat II. Due to budget constraints, they ended up making him a clone of Goro with tiger stripes instead.
It's possible that at one point Noob Saibot was going to be another female ninja, as there's a Dummied Out sprite in the game with black clothing that's associated with his move commands.