When you're on the play selection screen, you can hide the cursor so others can't see the play you choose. To do this, highlight the upper-left play (where the cursor is before you move it), then move Up on the joystick twice to hide the cursor.
Enter the following codes in the name entry screen with the following PIN codes to reveal a secret character...
At the Vs. screen enter the following codes. Note: The first number is Turbo, the second is Pass, and the third is Jump and the last is the direction to hold.