Mike Piazza's StrikeZone Codes -

Cheat menu:
Press L, R, L, R at the pre-game menu. Note: This code must be activated before the other pre-game menu cheats are enabled.

Devil's Thumb stadium:
Press Right, A, C-Up, L, A at the pre-game menu.

Super players:
Press B, A, R, B, A, L(2) at the pre-game menu.

Better throws by fielders:
Press B, A, L, Down, Z at the pre-game menu.

Better plays by fielders:
Press B, A, R, Down, L, B at the pre-game menu.

Faster fielders:
Press R, A, Z, L, Down, A, Z, L at the pre-game menu.

Better pitches:
Press B, L, A, B, R, Z at the pre-game menu.

Faster pitches:
Press R, A, Z, L, Down at the pre-game menu.

Crazy pitches:
Press C-Right, A, Z, C-Up, R, B at the pre-game menu.

Varied pitches:
Press C-Right, A, Z, C-Up, R, L at the pre-game menu.

Always hit home runs:
Press L, A, Down, R at the pre-game menu

Crazy ball:
Press C-Right, A, Z, B, A, L(2) at the pre-game menu.

Easy steals:
Press C-Left, A, Down, C-Up, Z at the pre-game menu.

Aluminum bats:
Press R, A, Z, B, A, L(2) at the pre-game menu.

Red bats:
Press R, Down, B, A, Right at the pre-game menu.

Blue bats:
Press B, L, B, A, Right at the pre-game menu.

Psychedelic bats:
Press Z, B, R, A at the pre-game menu.

Low gravity:
Press Up, R, A, L at the pre-game menu.

Increased gravity:
Press Up, Down, L, Up, R at the pre-game menu.

Fast game:
Press L, A, Z, R, B, A, L(2) at the pre-game menu.

Slow game:
Press Up, L(2), B, A, L(2) at the pre-game menu.

Alternate sky:
Press C-Right, A, Z, C-Up, L, R, Z at the pre-game menu.

Bonus teams:
Press C-Right, A, Down, Left at the title screen.

Hidden message:
Press C-Up, R, B(2) at the title screen.

View credits:
Press R, A, Z, R, C-Right, A, B at the title screen.

Hint: Beanball:
Hold the D-pad towards the batter while pitching to throw a beanball.

Hint Avoid beanball:
Press A to check your swing while a beanball is on the way to the plate.

Hint: Intentional walk:
Hold the D-pad away from the batter while pitching. The batter will walk after the pitch-out.