Same fighter match:
Select two player mode. Enter the character selection screen. Have player one highlight any character and press Down + B. The fighter's picture continue to be displayed with a dimmed name. Player two may now select the same character.

Easy mode:
Enter the options screen and set the level select to "Easy" and continue to "5". Enter the music select option and play 8C, 8B, and 8A. Enter the sound select option and play 90.

Difficult mode:
Enter the options screen and set the level select to "Hard" and continue to "5". Enter the music select option and play 8C, 8B, and 8A. Enter the sound select option and play 90.