Unlock Shy Guy:
Beat the Star Cup Singles/Tournment.
Unklock Diddy Kong Jr:
Beat the Star cup Doubles/Tournament.
Get Yoshi and Baby Mario Court:
Beat singles tournament with Yoshi.(mushroom cup).
Unlock Birdo Yoshi Court:Get Wario and Waluigi Court:
Beat the doubles star cup with Birdo.
Get Mario Bros. Court:
Beat singles tournament with Mario. (mushroom cup).
Get Donkey Kong Court:
Beat singles tournament with Donkey Kong.(mushroom cup).
Get Mario and Luigi Court:
Beat Singles Tournament with DK jr. (mushroom).
Get Pyranna Court:
Beat Pyranna Court with all 50 Balls.
Use Wario and beat the Doubles Star cup.
From Main menu select Special Games and then Ring tournaments Enter: LA98JRLAR. This code will unlock the Waluigi cup.
From the Main menu select Special games and then Ring Tournaments Enter: UOUFMPUOM. This code will unlock the Wario cup.
From the Main Menu, select Special Games, then Ring Tournaments. Enter "N24K8QN2P" to unlock the Bowser Cup.
From the Main Menu, select Special Games, then Ring Tournaments. Enter "48HWOR482" to unlock the Mariotennis.com Cup.
From the Main Menu, select Special Games, then Ring Tournaments. Enter "OF9XFQOFR" to unlock the Peach Cup.
Get Mario & Luigi Private Court:
If you beat the Star-cup doubles with Mario, you will get the private court of Mario and Luigi at the castle of Princess Peach.
After beating the Star Cup, hold the R button during character selection to make your character a Star.
From the Main Menu, select Special Games, then Ring Tournaments. Enter "ARM6JQARU" to unlock the Blockbuster Cup.
Unlock DK Cup:
From the Main Menu, select Special Games, then Ring Tournaments. Enter "MM55MQMMJ" to unlock the DK Cup.
The Ultimate Cup:
If you beat the star cup with all the players, you can unlock a special Star tournament which includes the Rainbow, Moonlight, and Planet cups
Be a Lefty:
Before choosing a character, hold the L button, and you can be left-handed.
To get your character power shot, hold the A button to hit the ball so hard, it will be harder for your opponent to hit back.
Unlock a Secret Tournement:
Unlock D.K. Jr. and Shy Guy. Beat the star cup singles with EVERY character. When choosing your player hold R so that a star is next to your name and click A. You have now unlocked the Secret Star Tournament.
Enter A3w5kqa3c as a password in the Special games menu to play a tournament for the Mario cup. Another password will be displayed after compleating the tournament. The new password is not acually a password for the game, but is for ranking you with other players at www.mariotennis.com.
In levels with Bombas in the back ground, if you hit the Bombas with a power shot they will explode.
See the Same Replay:
When showing a replay press B, and they will show the replay at a different angle.
Easily Start a Match Over:
When you are in a match and you are losing points, save the game and go to the main menu then go back to the game. Now the score will be 0 to 0. This is very good for beginners
Thanks to Revolution readers Jacob, Aaron Illingworth, brian riazzi, WaLuigi, link, Mathew Hoskins, RngrC127 192, Mike Schupska, masterd2t6, BOEFman and Mario Man!