Sega Sports Tennis

To unlock the King or Queen, win all of your matches in Arcade mode without using continues. If you're male, you'll face King. If you're female, you'll face Queen. Beat them to unlock.

To unlock King's Court, defeat the King and Queen in Mixed Doubles, in World Tour Mode (level 5).

On the Main Menu input L1, R1, L1, R1, CIRCLE, CIRCLE, CIRCLE, UP, UP, UP, DOWN, DOWN, DOWN. (Unverified)

Beat the level 4 Alien Force Volley training.

Complete Tank training at least till level 4 and you will get the special Tank Racket.