Dual Heroes
Change Medals into Gold Medals
When your level rank on your medal turns to 20 then your medal will automatically turn into a gold medal.

 Change Medals into
 Gold Medals

 Get Extra Uniforms
 Secret Characters
Get Extra Uniforms
Press the Z button when selecting your character. NOTE: This does not work in Practice and Story Mode.
Credit Goes To: Game Master (stapleton@n64cc.com) via N64cc

Secret Characters
Gyn - To earn the honor of playing as Gyn (Killer Sergeant), set the difficulty to Expert and beat the game in Story mode as any character.

Ray - Beat the game with Hana on the difficulty hard

Zorr - Beat the game with Juie on the difficulty hard
Credit Goes To: Cloud Master Materia via IGN 64