Depending on the specific ROM set (like the No-Intro or GoodGen sets), you will find one of the following inside:
The shape-shifting Shang Tsung and the four-armed Shokan, Goro. Mortal Kombat (World).zip
Johnny Cage, Kano, Liu Kang, Raiden, Scorpion, Sonya Blade, and Sub-Zero. Depending on the specific ROM set (like the