Cheat Mode
At girl select screen, press A, A, B, Right, A, Left, B, Down, A, Up, then select any girl and start the game. From now on, by pressing the A Button you will be able to select any mahjong tile to add to your pool.
Hidden Copyright Screen
In-game during the player's move on the second controller, press the sequence A, A, B, Right, A, Left, B, Down, A, and Up.