Bowser
Transfer from the N64 game
Bowser, Wario, Waluigi
Transfer N64 Mario Tennis data via Transfer Pak
Castle Court
Earn 60 points in Shooting Star Level 3
Drive Racket
In Varsity Class, have your spin 5 more than your power
Gold Racket
Talk to kid by lake, say no, then tap A and/or B 150 times
Jungle Court
Earn 60 points in Banana Bunch Level 3
Mario
Defeat Mario in the game
Peach
Defeat Mario/Peach in Doubles in the game
Silver Racket
Talk to kid by lake, say no, then tap A and/or B 100 times
Star Court
Earn all medals shown on Clear Status screen
Tropics Court
Earn 60 points in Target Shot Level 3
Warehouse Court
Defeat all Mario characters in Exhibition mode
Yoshi
Transfer from the N64 game