Christmas commentary - Set the system date to December 25 to hear Christmas commentary.
Dancing into the endzone - When your player is wide open, press L or R before running into the endzone and your player will do a dance.
Infinite creation points - Create a player, then go to "Edit Player" at the roster screen. Press Up or Down to choose the player you want to edit. Press Right to get to the speed category. Press A, then press A again.
New Year's commentary - Set the system date to January 1 to hear New Year's commentary.
Thanksgiving commentary - Set the system date to the third Thursday in November to hear Thanksgiving commentary.