Super player:
At the player creation screen, enter any of the development team names as a player name.

Automatic homerun:
While in the batters box, use the power swing. Then press Up + Left + L2 + R1 + X when the ball is thrown.

Big Heads:
At the MLB 2000 Start/Options menu, press R1, X, R2, and Select. You will hear a beep.

Bloopers Video:
Turn on the game, but don't press any buttons. Let the game run all the way through the introduction and the demo half inning of the game. After that, it will go back to the MLB2000 Logo and the bloopers video will start.

Easy Hits:
To get a easy single or sometimes a double you turn average to power and then you hold down and swing and hit the ball sharply to centerfield but sometimes you will ground into Double Plays.

Extra Out after Catching a Fly Ball:
Catch a fly ball and throw it to 2nd base. Then, throw the ball back and forth between the 2nd baseman and the shortstop (just keep pressing triangle). Eventually, one of the two players will throw it away into left center field. If you catch the ball with the center fielder, the umpire will say out as when you normally get an out.