Press Up+Down continuously for five seconds at the Today's Match-up Screen and then press any button. When the game starts you should be able to do the power slams.
At the Title Screen that says, "Press Start," enter Left, Up, B, Up, Down, Up, Right, C. Once entered, you can go to the Team Select screen. At the bottom of the list of teams you will find the hidden fraternity teams added on.
Go to the "Tonight's Match-up" screen. When the screen appears, start rotating the directional pad in a clockwise direction. When the announcer finishes speaking, while still rotating the pad, press the A button to start the game. When the tip-off appears, either you or your teammate will be a tornado.