Vaan's original name during development was Aqua, and he was originally written with a rugged and world-worn attitude. He was rewritten to be more effeminate after consideration of the game's target audience.
Contributed by Ricardoo_Suarez
Most of the Espers are based on the Lucavi in Final Fantasy Tactics, or other past bosses of previous Final Fantasy games. Twelve of them are associated with Zodiac signs.
Contributed by Outofmind23
The weapons that Gilgamesh carries are all weapons from past Final Fantasy heroes.
Contributed by PheonixGRX