When you complete the following tasks in Arcade mode the corresponding battle will begin.Unlock Secret 'Jade' Battle:
Get a double flawless victory and perform a fatality on Shang Tsung when battling against him. Unlock Secret 'Noob Saibot' Battle:
When you see Noob in 'The Temple' stage's background, win that battle without using 'Block'. Unlock Secret 'Reptile' Battle:
When a shadowy figure flies across the moon on 'The Pit 2 (Night)' stage get a double flawless victory and perform a stage fatality. Unlock Secret 'Smoke' Battle:
When Smoke appears behind one of the trees on 'The Living Forest' stage immediately press Down + Away repeatedly.