View all player statistics:
Press C-Up(2), C-Down(2), C-Left, C-Right, C-Left, C-Right, Start at the status screen.

Bonus stadiums:
Press C-Up, C-Left, C-Right, C-Up, C-Right(2), Z, C-Left, C-Right, C-Left, C-Right, Start at the stadium selection screen.

Delete saved game:
Turn on the game with a controller only in port two. Then, press Up, C-Up, Down, C-Down, Left, C-Right, Left, C-Right, Start