Highlight a golfer, then hold L2 + Select and press X at the character selection screen.
Alternate sounds
Press L1, R1, L2, R2, L1, R1, L2, R2, L1, R1 at the main menu. A sound will confirm correct code entry. Repeat the code to select various sound selections. Note: Press L1, R1, L2, R2, L1, R1, L2, R2 in the Japanese version of the game.
All golfers
Press L2, R2, L2, R2, Up, Right, Down, Left, L1, L2 at the main menu. A sound will confirm correct code entry. Note: Press L2, R2, L2, R2, Up, Right, Down, Left, L1, R1 in the Japanese version of the game.
Alternate ball (Japanese version)
Press L2 + R1 + Triangle while the swing meter is on screen before hitting the ball. Press Left or Right to change the ball's shape.