This is supposed to be it, It was under the user submitted cheats on here.
When you are in santa modesta go to the donut shop and press:
l2,l2,r2,square,circle,ieft,right,down,up,up,down.
(you have to be on top of the big donut).
P.S: helps if you don't blow the whole city up.It will take you to an alien planet where humans attack YOU.
When things go bump in the night...
Bump back.