Nintendo Ring Tournaments
Select the "Special Games" option at the main menu, then choose the "Ring Tournament" selection. Enter one of the following codes to play in the corresponding tournament for the indicated Cup. Note: Another code will be displayed after completing the tournament. The new code is not actually a code for the game, but is for ranking you with other players at Nintendo's Mario Tennis web site.

Mario Cup
Enter "A3W5KQA3C" as a code at the code entry screen to play a tournament for the Mario Cup.

Wario Cup
Enter "UOUFMPUOM" as a code at the code entry screen to play a tournament for the Wario Cup.

Luigi Cup
Enter "M1C2YQM1W" as a code at the code entry screen to play a tournament for the Luigi Cup.

Waluigi Cup
Enter "LA98JRLAR" as a code at the code entry screen to play a tournament for the Waluigi Cup.

Nintendo Power Cup
Enter "J6M9PQJ6U" as a code at the code entry screen to play a tournament for the Nintendo Power Cup.

Left-handed character
At the character selection screen, hold L while selecting a character to make them left-handed.

Handicap
Win the Star Cup with a character. Then at the character selection screen, hold R while selecting that same character to make them have handicaps and be more powerful. If done correctly, a yellow star will appear in the bottom right of the screen (for player one) or bottom left of the screen (for player two). Press L + R to have a left-handed player that is also a star character.

Play as Shy Guy
Win the Star Cup/Singles Tournament.

Play as Donkey Kong Jr.
Win the Star Cup/Doubles Tournament.

Donkey Kong court
Win the Mushroom Cup/Singles Tournament with Donkey Kong.

Yoshi/Baby Mario court
Win the Mushroom Cup/Singles Tournament with Yoshi.

Birdo/Yoshi court
Win the Star Cup/Doubles Tournament with Birdo.

Mario/Luigi court
Win the Mushroom Cup/Singles Tournament with Mario.

Mario Brothers court 2
Win all the Doubles Tournament Cups with Mario. Note: This is another Mario Brothers Court, but not the alternate way to get the previous one.

Mario/Luigi Castle court
Win the Star Cup Doubles and Singles Tournament with Mario.

Wario Brothers court
Win all the Doubles Tournament Cups with Wario.

Piranha Plant court
Note: This court only works in Piranha Plant Challenge. Complete any court (perfect, all 50 balls) in the Piranha Plant Challenge with any character.

Special Cups
Win all the Tournament Cups with all the characters (including Shy Guy and Donkey Kong Jr.) to unlock the Special Cups, which are much harder than the previous ones. Press R while selecting a character at the character selection screen to access the Special Tournament in the menu. The three Special Cups in order are Rainbow Cup, Moonlight Cup, and Planet Cup. Once you win a Cup, you will move onto the next one.