From Wikipedia
PlayStation
There were at least three public revisions of this game for the PlayStation (the final version was the North American Greatest Hits and European Platinum edition). With each revision, aspects of the gameplay were refined, producing gameplay closer to Ultimate Mortal Kombat 3 for the Arcade. Many of the infinites and bugs found inthe game only existed in earlier revisions. Shang Tsung never appears anywhere within the "Choose Your Destiny" towers, probably because of the loading delays when morphing in the PS version (there's an option that lets the system load two additional characters into memory when playing as Shang Tsung, eliminating the long loading delays of MK3 and UMK3 when morphing); the only time the CPU ever controls Tsung is during the attract mode. After beating the PS version of the game, the final message in the credits says "MK4 coming in 1997".