Add one run to home team
While playing the game, hold L + R + Z and press C-Left(2).

Add one run to away team
While playing the game, hold L + R + Z and press C-Right(2).
Three ball count
While playing the game, hold L + R + Z and press Up, Down.

Three outs
While playing the game, hold L + R + Z and press Down, Up.

Hit a homerun
While in the batter's box, hold L + R + Z and press Left, Up, Left, Up

Strike out the batter
While on the pitching mound, hold L + R + Z and press Right, Up, Right, Up.

Easy homeruns
While in the batter's box, hold Analog-stick Up/Left and press B. If positioned correctly, the batter will hit a homerun most of the time.

Homerun sounds
While running around the bases after hitting a homerun, press C-Up to hear a soft horn, C-Right to hear a loud horn, or C-Down to hear a whistle.