Hold L + R + X + A on controller two, then press Start on controller one at the options menu.
Press X, A, Y(2), A, Y, X at the ‘Start’ menu.
Press X, Y(3), B(2), X, A, B at the ‘Start’ menu.
Press X(2), A, B, Y, A, Y(2) at the ‘Start’ menu.
One hit kills:
Press X(5), Y, B(2), A, B, A, B at the ‘Start’ menu.
Hint: Level 1-1: Defeating the sewage area Boss:
At the end of level 1-1 you will meet up with the Boss alien of the sewage area. After a fast eight or nine seconds of the alien being submerged, hold down your laser button. When he rises from the aquatic sludge, turn in his direction and release the button.