Red belt:
Press A, Down(2), B(3), C, Left, Right at the title screen.

Green belt:
Press A(2), Down, C, B, A, Up(2), Down at the title screen.

Hyper mode:
Press A(9) at the title screen, then begin a match in two player mode.

Alternate Crusher appearance:
Select one player mode, then press C(3), B(3), A(3), C, A, B at the title screen. Then press Up for a green body or Down for different horn colors.