Play Luigi's Shooting Star mini-game and win both levels. When you get to the third level, beat the high score of 60 to unlock the Castle Court in linked play and exhibition modes.
Play Baby Mario's Target Shot mini-game and win both levels. When you get to the third level, beat the high score of 60 to unlock the Tropics Court in linked play and exhibition modes.
Play Donkey Kong's Banana Bunch mini-game and win both levels. When you get to the third level, beat the high score of 60 to unlock the Jungle Court in linked play and exhibition modes.
Play Mario's Boo Blast mini-game, complete levels 1 and 2, and beat the high score to unlock the Star Court.
If you lose a game in RPG mode, pause the game immediately before the score appears. Save the game, quit, then resume the game you were just playing. The game (not match or set) will be reset.
Play as Students
Defeat the students you face in the Junior, Senior, Varsity, and Traveling Leagues to unlock them at the character selection screen.
Play as Mario
Successfully complete the game in Singles.
Play as Peach
Successfully complete the game in Doubles.
After making it onto the varsity traveling team, go back to the Training Center. Get the Iron Racket. Next, go to the Training Courts and go up to the upper right of the area where the lake is. There will be a boy there practicing his swing. He will say that he is swinging quickly and will ask if you agree. Say "No." He will then tell you to swing. You automatically swing slowly. He then says that you are slow and leaves. You're then backed up to the lake and the game will tell you to hit "A" as many times in 10 seconds as you can.
The secret to winning this is to put a soft blanket or towel between your finger and the "A" and "B" buttons, and to quickly slide it over both "A" and "B" as fast as you can. If you get between 100 and 149, you will get the Silver Racket from the water sprite. If you get 150+, you will get the Golden Racket.
Status of rackets:
Silver: Serve -1, Stroke -1, Volley +3, Angle +1, Placement +1
Gold: Serve +2, Stroke +2, Volley -1, Angle -1