Unlock Patapata (Paratroopa)
To unlock Patapata (Paratroopa), just beat the 3 tournaments of the Normal Cup in doubles.

Unlock Propera Hey-Ho (Fly Guy)
To unlock Propera Hey-Ho (Fly Guy), just beat the 3 tournaments of the Normal Cup in singles.

Unlock Boss Packun (Petey Piranha)
To unlock Boss Packun (Petey Piranha), just beat both Special tournaments (Fire and Thunder) in doubles.

Unlock Hana-Chan
To unlock Hana-Chan, just beat both Special tournaments (Fire and Thunder) in singles.

Star Cup
To unlock the Star Cup, just beat the 3 tournaments of the Normal Cup.

Max difficulty level
To unlock the MAX difficulty level, just beat the 3 tournaments of the Star Cup.

Yoshi's Defensive Power Shot Color Change
Beat Flower Cup doubles with any character

Event Mode
At Mario Tennis title screen hold Z button while pressing start to unlock Event mode. This is a tiebreak game, you are able to select from 3,5, or 7 points. This does not remain unlocked however, you must do the code every time.

Get a character's star
To get a character's star version, just beat the 3 tournaments of the Normal Cup with a character and you will get the star for this character.

Ace COM skill level
To unlock the "Ace" Computer skill level for exhibition, defeat
Planet Cup in either Singles or Doubles mode.

Bowser Court
To unlock the Bowser court, just beat the Fire tournament of the Special Cup in singles.

Mario Bros Court
To unlock the Mario Bros court, just beat the Thunder tournament of the Special Cup in doubles.

Special courts options
To unlock all the options of a special court, just play on that
court in the Special Cup.