Mario Tennis

In-game reset:
Press A + B + Start + Select during game play.
Information in this section was contributed by Jmarco5.

Hint: Walk faster:
Hold B while walking.
Information in this section was contributed by Y2JerichoHALic55.

Castle Court:
Play Luigi's Shooting Star mini-game and win both levels. When you get to the third level, beat the high score of 60. You can now play on the Castle Court in linked play and exhibition modes.
Information in this section was contributed by AaronCastle.

Tropics Court:
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. You can now play on the Tropics Court in linked play and exhibition modes.
Information in this section was contributed by AaronCastle.

Jungle Court:
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. You can now play on the Jungle Court in linked play and exhibition modes.
Information in this section was contributed by AaronCastle.

Star Court:
Get every Medal and Gold Trophy in single player mode. After that, you must win Mario's Mini Game, Boo Blast's High Score. The Star Court will now appear at the course selection screen.
Information in this section was contributed by AaronCastle.

Wario Warehouse court:
Defeat all the Mario characters in exhibition mode, including the Nintendo 64 characters.
Information in this section was contributed by BLaZedBaLLeR.

Play as Students:
Defeat the students you face in the Junior, Senior, Varsity, and Traveling Leagues to unlock them at the character selection screen.
Information in this section was contributed by AaronCastle.

Play as Peach:
Complete the game in Doubles
Information in this section was contributed by AaronCastle.

Play as Mario:
Complete the game in Singles
Information in this section was contributed by AaronCastle.

Nintendo 64 characters:
Use the Transfer Pak with the Nintendo 64 version of Mario Tennis. Select "Transfer" at the main menu, then select "Game Pak Check". After it checks, an icon that says "Transfer N64 Characters" will appear. This will allow you to play as Bowser, Waluigi, Wario, and Yoshi.
Information in this section was contributed by AaronCastle.

Silver and Gold Rackets:
Make sure you have the Iron Racket equipped, then go to the training courts. Go up to the lake and follow it until you see a boy practicing his swing. Tell him you do not like it and you will show him your swing. He will laugh, and you will get angry. Next, get ready to swing. In ten seconds, press A as many times as possible. If you press it 100 times, you will get the Silver Racket. If you swing it 150 times you will get the Gold Racket. Note: Try wrapping your hand in your shirt and rub it over A until it ends. You should be able to get either racket this way.
Information in this section was contributed by pickleddevil.

To get a Gold Racket easily, once you get the Iron Racket, equip it and go to the lake at the training court. There should be a boy swinging. Talk to him and say that he has a bad swing. You will now be able to swing for ten seconds. You are instructed to tap A as fast as you can, but you can also press B. Get a friend to help you, with one of you pressing A and the other B.
Information in this section was contributed by Young Wang.

Spin Racket:
In order to get the Spin Racket, on the screen that displays the stats of your power, spin, speed, etc., you need to have five more on your spin than your power. When you get the racket, press B to hit a curvy shot.
Information in this section was contributed by lenny and andrew.

More mini-games:
Unlock the Nintendo 64 characters, then check the mini-game screen. More entries should be available. To unlock even more mini-games, win the Junior, Senior, Varsity, and Traveling Leagues in Singles and Doubles.
Information in this section was contributed by AaronCastle.

Game reset:
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.
Information in this section was contributed by Matt Provencher.

Hint: Playing in any of the training rooms, competitions, matches, etc.:
When you are on the court, position yourself in the center (or just slightly behind center ) when playing. This allows you to be able to move quickly to any position on the court, because you are the same distance from any point. After a return or serve, go back to that position to prepare for a return ball. This will help you greatly in your advancement and allow you to win and return more balls, giving you more experience points, and allowing you to dominate the court more.
Information in this section was contributed by Brandon Tumangday.

When playing against an opponent or in the training, read where the ball will be going. If the opponent or the machine goes to one of the upper or lower corners, position yourself between the center of the court and the sideline closest to where the your opponent is positioned. This will allow you to return the ball easily if it goes to the sideline or to the center of the court. The same thing works if the opponent goes to the upper center or lower center. If upper, stand in the center because you will have enough time to react because of the distance. If the opponent comes close, go back slightly to get more time to react.
Information in this section was contributed by Brandon Tumangday.

When playing on the Wall trainer, if you stand close and can react quickly, you will be able to return the ball rapidly to the wall, allowing you to get the 50 returns goal quicker: Note: This will not always work; it depends on how quickly you can move and hit the ball without hitting the rotating pads and alternating high and low returns. This is most difficult when you reach the higher levels where there are faster and more pads to avoid. When you get to the higher levels, stand about center back and alternate high and low hits. This will work most, but not all of the time. Just remember your ball return power. The speed will also be a determining factor in how you can control and receive the ball
Information in this section was contributed by Brandon Tumangday.

When you finish all four levels in both training rooms, your next goal will to beat your previous record. When you get to your highest number of returns, beat it by one and then miss the ball. This should give you good experience points, but allow you to keep playing it for awhile since your goal each time will be just one higher.
Information in this section was contributed by Brandon Tumangday.

Hint: Always win:
Select adventure mode. If the score is 40-0 for your opponents, save and quit. When you restart the game, it will be 0-0 again. The game only counts games and sets.
Information in this section was contributed by chris gallant.

Hint: Easy wins:
Try to do a drop shot, then run up to the net and hit the ball from side to side (after they hit the ball). You should get a point after the third or fourth hit.
Information in this section was contributed by MRSOCCER333.

Hint: Always the Island Open Tournament:
Get to the Island Open Tournament. Immediately press A + B + Start + Select when the match starts to win that round. Repeat this four times to instantly win the tournament.
Information in this section was contributed by greg.

Hint: Drop Shot technique:
Note: This trick only works in singles. When doing a tough match (for example, Island Open against Mario), get close to the net and use the drop shot (B + A) to lure your opponent close. Then, when they are close and return the shot, hit the ball to either side. They may dive and hit the ball, but it will be weak. Smack the ball again when they are trying to get up.
Information in this section was contributed by Glover2002.

Hint: Smash Ace:
When you are in a singles or doubles match, you can do a Smash Ace when you see a yellow circle. Go on the circle and press B + A.
Information in this section was contributed by BigBen3480.

Hint: More experience:
After you have completed all of the wall mini-game levels, talk to the girl in front of the door that is preventing you from walking in. She will ask you if you are ready for the master level of practice. Press B and she will ask if want to try for an even easier level of practice. Answer "Yes". Then, walk on any of the level numbers and press A. You will get more experience.
Information in this section was contributed by Matt.

When you enter the traveling team in singles mode, you will have new equipment. Go to the training center and equip the Iron Shoes or the Iron Racket. They both give you 150% more experience when you win a match.
Information in this section was contributed by Ukato372.

Hint: Choose partner:
Finish either Mario Challenge (singles is easier if you use the "Drop Shot" trick technique). After that, make sure you have an empty file or one you do not use. You now have the option to pick either Harry or Kate (and make them left or right handed).
Information in this section was contributed by Glover2002.