When asked to select a world, choose the lower leftsquare on the display. Shoot the large cow skull on the groundin the first scene. When you lose a life or shoot a hostage, thefinal scene from Mad Dog McCree will be displayed instead of thenormal sequence.
Rescue the commander. After you enter the transporter, choose the TV monitor at the lower-left corner of the screen. When you arrive at that scene, you'll see a cow skull. Shoot it several times to unlock the hidden scene.