Here are the game's three unlock codes for Scorpion and Sub-Zero in Ko-op and Vs. Mode and the hidden Mortal Kombat II arcade game. All of the kodes are to be entered fairly quickly on the Main Menu screen. You will hear a confirmation sound once the code is entered sucessfully.
<table border="0" align="center"><tr><td width="50%" class="story_text"><span style="font: 12pt Arial Bold;color:lime;">Xbox</span>
Unlock Scorpion
(Hold White Button at Main Menu)
X, Up, L trigger, R trigger, Left, Right, X
(Release White Button)
Unlock Sub-Zero
(Hold White Button at Main Menu)
X, Down, Up, L trigger, L trigger, Up, X
(Release White Button)
Unlock Mortal Kombat II
(Hold White Button at Main Menu)
X, Up, Down, Right, Left, Black, X
(Release White Button)
</td>
<td width="50%" class="story_text"><span style="font: 12pt Arial Bold;color:#4444FF;">PlayStation 2[/b]</span>
Unlock Scorpion
(Hold L2 Button at Main Menu)
Square, Up, L1, R1, Left, Right, Square
(Release L2 Button)
Unlock Sub-Zero
(Hold L2 Button at Main Menu)
Square, Down, Up, L1, L1, Up, Square
(Release L2 Button)
Unlock Mortal Kombat II
(Hold L2 Button at Main Menu)
Square, Up, Down, Right, Left, R2, Square
(Release L2 Button)</td></tr></table></center>
<table border="0" align="center"><tr><td width="50%" class="story_text"><span style="font: 12pt Arial Bold;color:lime;">Xbox</span>
Unlock Scorpion
(Hold White Button at Main Menu)
X, Up, L trigger, R trigger, Left, Right, X
(Release White Button)
Unlock Sub-Zero
(Hold White Button at Main Menu)
X, Down, Up, L trigger, L trigger, Up, X
(Release White Button)
Unlock Mortal Kombat II
(Hold White Button at Main Menu)
X, Up, Down, Right, Left, Black, X
(Release White Button)
</td>
<td width="50%" class="story_text"><span style="font: 12pt Arial Bold;color:#4444FF;">PlayStation 2[/b]</span>
Unlock Scorpion
(Hold L2 Button at Main Menu)
Square, Up, L1, R1, Left, Right, Square
(Release L2 Button)
Unlock Sub-Zero
(Hold L2 Button at Main Menu)
Square, Down, Up, L1, L1, Up, Square
(Release L2 Button)
Unlock Mortal Kombat II
(Hold L2 Button at Main Menu)
Square, Up, Down, Right, Left, R2, Square
(Release L2 Button)</td></tr></table></center>