If you recall the back-up technique, it can be used in VS mode when on Offense. This can only be done when your friend has the ball, and you help you friend advance. When your friend is about to take a shot, be ready to hold L near the opponents to stop them from charging their jump or jump to block the ball. You will push them over and this will cause no foul.
To enable Mortimer Mouse, win the Level 2 tournament in Challenge Mode.
To enable Pete, win the Level 3 Tournament in Challenge mode.