Within Mortal Kombat: Shaolin Monks finding Secret Orbs will sometimes net you a new character for versus mode. Scorpion can be unlocked in Story Mode if you beat the game with Liu Kang. Subzero is available for single player mode and co op Mode if you beat the game once with Kung Lao. Otherwise, you need to use your wits and perception of game mechanics to reach hidden areas to unlock the rest of the characters. Here is how you do it.

Unlock Reptile

Living Forest. Go to the section after the Brotherhood of Shadow. Long Jump across the gap with the tiny waterfall. Go through the door. Now, get the Clay Statues to come to life. Destroy their shield. You only need 1 of them. Now, get one of them over near the Giant Stone Column on the other side of the stream. It's the stone column right near where you entered. Throw the Clay Statue into it! It should come crashing down. Now, return to where the little waterfall was. There is no longer a waterfall. Just a Koin that contains Reptile.

Unlock Baraka

Go to the area where you have to wall climb, in the soul tomb portal. You will see two paths, one leading left, the other to the right. The right path has a statue. Use fist of ruin and break it. Keep going and use the long jump ability across the gap and you will get him.

Unlock Johnny Cage

In the Wu-Shi Academy where everything is burning, go to the very right of the gate and jump on the roof of the house. Run to the right and jump. If you did it correctly, you will be on a new platform with a boulder blocking your way.

Unlock Kitana

In the MK2 arena level (right before the portal with the two statues in front of it) in the evil monastery, you will see many pillars. Jump on one of them which is half broken and then double jump onto the roof. You will find the secret there.

Unlock Scorpion

In foundry, follow the pathway downstairs to the left of the save station. Two archers will bust through the wall. Throw one at the wall to the left of the door way and it will bust open revealing a secret room full of lava and a ying yang on a ledge. Grab one of the archers and throw them in the lava. Then, double jump off the guards back to claim the Scorpion ying yang for VS.

Unlock Sub-Zero

After taking the boat ride across blood lake, his VS. icon is in back of the lion looking statue to your left (facing the big door), just run along the wall and when you get to the end, double jump and it's yours.

Unlock Mortal Kombat II

Locate and clear all mini-missions issued by Smoke.

- Break Walls in the Soul Tombs to reveal a secret fatality. This is an area with spikes on the ceiling and about 6 Tarkata in the room. You can see out on the far side of the room and you need to break the four center sections of the wall.

- Destroy a statue in Wu'Shui academy and enter the Warrior Shrine. The Warrior Shrine is at the VERY start of the Wu'Shui area.

- Offer 3 Sacrifices in the Sacrifice Room in Soul Tombs. You need to go through the room that doesn't have a green or red symbol above it and then do air throws to get the Tarkatas into the spiked areas.

- To unlock the Portal, find all Purple Portals and throw an enemy into each one. There are only 2 portals to throw mobs into. One is near the Evil Monastery and one is at the lower level near the climbing spot.

- To unlock the Pit II, enter the Portal and survive in the frozen peaks.
After you enter the portal you just need to keep killing the guys that show up until it says you've won. We found that tossing them off the side seemed to prove quite useful and then just killing one when you need to recharge your life a bit.