This has no purpose other than a laugh, and will not unlock anything in the game. Enter practice mode (or two-player duel if you want to play with a friend) and choose your characters and stage. When the fight starts, put as much distance between you and your opponent as possible. If in practice mode, set the opponent's action to Deflect-Back at the pause menu. Once you are as far away as desired, launch an energy ball by pressing Circle. In practice mode, your opponent should knock it back at you. Just before the ball hits you, press guard (X) and if it timed correctly, it should be reflected back at the opponent. In a two player match, you can play it like a proper game. For example, flip a coin to see who serves (launches the energy blast). Set a score limit. If the Ki ball is knocked away, hits, or is hit by another Ki blast, whoever reflected the ball last gets the point.