At the character selection screen, hold L1 or R1 and select a character.
King's Court
Defeat King and Queen (mixed double) level 5 in world tour mode to unlock King's Court. This level 5 will only be available if you won the mixed double match in level 4. Both matches will be in December.
Play as King or Queen
Win all matches without using any continues. If using a male character, you will face King. Otherwise, you will face Queen. Defeat them to unlock them as playable characters.
Special rackets
In the world tour mode, defeat opponents in level 3 and higher without losing a set. If you win a straight set you will get a special racket in every championship that you won.