Pocket Tennis Color

Highlight a character on the selection screen, then press B.

Instead of hitting A to pick your tennis pro, use the B button.

Defeat the three opponents in the first tournament in tournament mode to unlock an amoeba player which turns into a racquet when hitting the ball.

Defeat your opponents for the Aries cup in tournament mode to unlock a fat player.

Alternately, win four tournaments.

Press Down before serving, to bounce, toss, or do something else the ball (depending on your character). There is only one animation per character, but most characters' animations are unique.

For a character not of this world, defeat the 3 opponents in tournament mode. You'll now have access to a new character called Amoeba.