New Stadiums and Other Codes

At the stadium select screen press:
R1,L1,R2,L2,R1,L1,R1
You should hear an announcer say "Triple Play 99" and have The Colliseum, Neo-Vancouver, and Anytown USA as stadiums!

In a game, press and hold all four shoulder buttons, then...
Powerful Homerun: Triangle, Square, Triangle, Circle, X , Square, Left, Right during at bat.

Easy Strikeout: Up, Down, Triangle, Square, Triangle, Circle, X, Square during at bat.

For commercials press left, square, right, circle

For announcer stories press up, triangle, right, circle

For an overlay graphic with a fact about the batter press left, square, up, triangle (you might have to do this twice)