Completion bonuses
Successfully complete and save the game to unlock the "Unknown" difficulty, very hard difficulty, "Sound Test" option, and "Game Record" option. Start a new game with a cleared game file to have access to the "Grade Shop".

Final Fantasy 7 reference
During game play you will learn of the underworld know as the Qlipoth. However, the trees that hold the over world up are called the Sephiroth.

Tales Of Symphonia reference
Go to Daath after you defeat Mohs in the Radiation Gate. Go into the Chapel and talk to the replica twice. The second time you talk to him, he will say, "........Ze....los..... Di..ed..." The person that he is referring to is Zelos from Tales Of Symphonia.

Get Asch in your party permanently
On the OverWorld, when you not doing any loading, open the disc tray and remove the game disc. Shut the disc tray. Without the game disc, you can go anywhere on the OverWorld. Once you got to the desired spot, open the disc tray and put game disc back in. Close the disc tray. You can now get Asch on the Albiorl and leave Luke forever in the Mushroom Road. Note: You will lose Luke if you do this.