To activate debug mode, first you must start a game normally. 
At the character select, hit right on the joystick 3 times, 
then left all the way to Lupas (select Lupas). When you start, 
hit C-right, C-right, C-right, C-left, C-right, C-right, C-up, 
C-up, C-up. If you do it correctly you will hear a noise that 
sounds like Lupas barking but he won't be moving. To use this 
cheat, after the bark, just go through the items and weapons 
you want to change into by tapping A. Hit A once, it changes, 
hit A again, it changes. just cycle through till you have 
found what you want. Then hit B to place that object/item where 
Lupas is standing.