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:
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.

Get Wario and Waluigi Court:
Use Wario and beat the Doubles Star cup.

Waluigi Cup:
From Main menu select Special Games and then Ring tournaments
Enter: LA98JRLAR. This code will unlock the Waluigi cup.

Wario Cup:
From the Main menu select Special games and then Ring Tournaments
Enter: UOUFMPUOM. This code will unlock the Wario cup.
Bowser Cup:
From the Main Menu, select Special Games, then Ring Tournaments.
Enter "N24K8QN2P" to unlock the Bowser Cup.

MarioTennis.com Cup:
From the Main Menu, select Special Games, then Ring Tournaments.
Enter "48HWOR482" to unlock the Mariotennis.com Cup.

Peach 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.

Star Players:
After beating the Star Cup, hold the R button during character selection to
make your character a Star.

Blockbuster Cup:
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.

Power Shot:
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.

Ring 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.

Detonate Bombas:
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