Green ? Menu: Go to the OPTIONS menu and hold
Up + L + R until the screen shakes. This should allow you to access the green ? mark menu. Here you can enable one button fatalities, normal boss damage and a few other cool tricks.
Red and Blue ? Menus (Japanese version) At the story screen press HK, LK, RUN, LP, HP, HP, HP, LP, LP. If done correctly you will hear "OH-MAW". The lets you enable freeplay, change the fatality time, and much more.
At the start screen where you see the skeletons, type in crazycyrax on your
controller (C, Right, A, Z, Y, C, Y, Right, A, X). If this is done right, you will hear a sound.