Quan's Dwelling: After the events on Disc 3 at Alexandria castle, you'll be able to do this small sidequest. With both Vivi and Quina in your party, head to Quan's dwelling. There, Quina, like always, will start thinking about food, then a conversation will comerse outside that gives a little insight on Vivi and Quina's pasts. After the conversation if you search around the clock you'll get the accessory, Running Shoes!
Ruby Bursts In At the beginning of the game in the Prima Vista you'll have a conversation with Baku about kidnapping the Princess. If you select "...to kidnap Queen Brahne" around 65 times, Ruby will burst in and scold the Tantalus gang. Very funny hidden scene!
Final Fantasy Music: Whenever you return back to Gaia after going to Terra, head to the Treno Action house and pick up the Doga's Artifact and Une's Mirror. After you do so, go back to the Black Mage Village and talk to the Black Mage that is standing near the phonograph at the Inn. When you talk to him, the background music will change to a song from the Final Fantasy III soundtrack.
Nero Brothers' Gambling: On Disc 3 at the beginning when the gang is in Alexandria, when you get control of Zidane you'll be able to talk to Benero, Genero, and Zenero, also known as the Nero Brothers. They will ask you if you want to play a game like the shell game. You can win a maximum of 25,600 gil playing this game! Pretty nice way to make money if you are low on cash.
Eidolon Wall - Garnet's Real Name: On Disc 4 you'll be able to uncover one of the game's largest secrets for yourself! Just head to Madain Sari. When you get there, make sure to have a party with Dagger in it. Then, head to Eiko's back porch and Lani should be standing around. But when you do get there, Lani will run away quickly.
After doing so, exist and have anyone in your party besides Dagger ot Amarant. Talk to Lani twice. After reading the message, head to the Eidolon wall. Walk clockwise from the entrance and return back to the entrance. Move just past the "!" bubble that pops up until you hear a small sound. After you do, walk counterclockwise back to the entrance once again, just past the "!" bubble on screen. Do this all again 9 times!! Make sure that each time you do so, you hear the sound at the wall. On the last time around the HP and MP of the character's will be restored.
After all that work there is still one last thing you must do. You must read all the paintings. A bunch of extra messages will appear, and when you are finished, go back to Ifrit's drawing and look around for an additional message that will reveal Dagger's real name!
Blackjack: There is an aditional little game you can play at the end of the game after the credts roll. When you see the words "The End," enter the following sequence of buttons: