Hidden Characters (American Version): 

Enter these codes at the title screen when 
'Press Start' appears.

Kron: L2, L2, Up, Up, Up, Left, Down, Up, 
Circle, L1 

Hidden Characters (European Version): 

Enter these codes at the title screen when 
'Press Start' appears.

Kron: Up, Down, Up, Down, Triangle, Left, 
Right, Left, Right, Circle, R1, R2

Bimorphia: Right, Right, Right, Down, Square

Juni: Up, Left, Left, Up, Square

Khan: Up, Up, Down, Down, Triangle

Moloch: Up, Right, Down, Left, Square

Mongwan: Down, Down, Down, Up, Triangle

Redempter: Up, Down, Left, Right, Circle

Stygian: Left, Right, Left, Right, Triangle

Vodu: Left, Left, Left, Up, Circle