In Mortal Kombat (aka Mortal Kombat 9, 2011 version) for the PS3 and Xbox 360, you can fight Classic Jade as a Hidden Kombatant in Arcade mode to earn the hidden You Found Me! achievement/trophy.
To find Classic Jade, you need to go through the entire ladder without losing a single round, then get all flawless victories, and a Fatality on the Shang Tsung fight. After he dies, Jade will come out to fight you on the Goro stage.
This is best done on beginner, and it will still not be easy. It must also be done with a minimum of two round matches, however the round time can be lowered. If you get hit by Shang Tsung, beat him to the point that it says “Finish Him” before you select a new fighter, or else it will count as a loss and you won’t fight Classic Jade.
Check out my other guide if you’re looking for the other Hidden Kombatants for achievements or trophies.
