Pause the game and enter the following.
Code: X, Y, X, X, Y, Y X, Y, X, X Y, Y
At the episode selection screen enter the following.
Code: X, Y, Y, X, X, Y, X, Y
Unlock 9320 Battle Droid
Get all the gold in the Light Campaign to unlock the 9320 Battle Droid.
Get all the gold in the Dark Campaign to unlock Fetica .
Unlock Stone Gnome
After finishing the Dark Campaign you will unlock the Stone Gnome.
Unlock Earth Golem
After finishing the Light Campaign you will unlock the Earth Golem.