Bonus characters and court
At the Smart Dog logo screen, press Up, Down, Left, Right, Start. If you entered the code correctly, you will hear a voice say "Yeah." Then, additional characters and the Canyon court will be available in "Smash Tennis" mode.
While playing a game, hold R1 + R2 and press X, Square, Circle, Square, X, Triangle. Then release R1 + R2, and press Select.