Blackjack Mini Game
After you finish the game, allow the credits to finish and wait a little for the game of blackjack to appear.
Two Player Mode
Here it is folks, tested and approved by me (SolidSnake), the very simple operation that lets you play FFIX with two-players. Here is what you do, pull up the menu with the Item, Ability, Equip, etc options. Select the CONFIG option, scroll down to Battle Control, select Custom and now you will be able to make whatever character you want to be controlled by the second player. For instance you can set player-one to control Zidane and Vivi, while player-two will control Garnet (Dagger) and Steiner. This only affects the random/boss battles, so don't expect to have a full co-op two-player mode.