Note: This only works in a regular game. When you are about to throw your ball, release B when the Wiimote is all the way behind you. You should throw the ball backwards, and all the Miis will cheer.
When you are in a normal game of bowling, put your hand with the Wiimote up, hold B, and swing your hand down. When your hand is behind you, release B. The ball should go behind you and if it reaches the Miis they will jump up, spin around a few times, and land while saying "Ow!"