The following are known Action Replay Codes for Mortal Kombat 3 on Nintendo Game Boy / Color (GB / GBC). These codes were also known as GameShark Codes and in most cases will work on both devices.

Device Compatibility: Action Replay & GameShark

Infinite Time
0109dfc0

P1 Infinite Health
0ff14cd

P1 Infinite Lives
0103dbd4

P2 No Health
010154cd

Player 1 Is Shao Khan
0109ced4