Play Hidden Teams
While holding L button, select Pre-Season game with A button. Now, scroll all the way to the right. Three new teams will be playable: Nintendo, N64 and Left Field.
Wrong Players in Replay
Get into any type of game -- it doesn't matter. Do anything in the game, with anybody, and then get it so that you can substitute players into the game. After you substitute the players in, go to replay mode and go back to any point in the game where you had the original players in. Say you had Shaq in, and he did a monster dunk, and then you substituted Dickey Simpkins (bad player) in for Shaq. In replay mode, Dickey would be doing the monster dunk Shaq had been doing, even though he hadn't been in the game!
Hang on Rim
Whenever you do a two hand dunk just hold the B button and you'll hang on the rim. But don't hang for a long time or you'll get a technical foul.
To hang on the rim hold the B button
To change players in the replay do anything you want with who you want, go to substitutions and change the player you were replaying to somebody else. Go back to the replay and it will be a wrong player. To get three secret teams hold the L button and go into pre-season by pushing the A button, go left and there will be three new teams. What they are you will have to find out.
At the start up screen push these buttons to make the players head look like they are aliens: C-Up, C-Down, C-Left, C-Right, Start, Start, A, B, A, R, and Z!
NOTE: THIS ONLY WORKS FOR THE LEFT FIELD TEAM!
When playing pre-season press start and press A, C-up, D-pad Down, D-pad Up, C-down, R, R, B, C-right, C-right, Z.