Talk to her in the Casino as Sonic after finishing Sky Chase.
Big
Defeat Chaos 6 as Sonic.
E-102 Gamma
Defeat Gamma after finishing Sky Deck as Sonic or Tails. An alternate way to unlock him is to finish Twinkle Park as Amy and watch the FMAs after it.
Easy rings for Black Market
After obtaining the Light Shoes (and Crystal Ring to speed up the process), go to the Casino area and step on the button to make the rings appear. You can do this repeatedly for more starting rings. Note: The ring limit can exceed 999, but you cannot tell exactly how many you have. Listen for the extra life sound to keep track of them. When you are satisfied, go to Emerald Coast and complete the level without getting hit. You will be awarded with however many rings you collected at the end. Go to the Chao Garden, then the Black Market, and spend your hard earned coins.
Knuckles
Defeat him after finishing Ice cap as Sonic or Tails.
Light-Speed Shoes
The following item can be unlocked in Playstation Home. Unlock the light-speed shoes in-game, then upon loading the savefile after booting the game a second time it will unlock in Playstation Home.
Miles Tails Prower
Finish the C mission of Emerald Coast action stage as Sonic.
Play Emerald Course in chao race
Beat the rest of the four courses. Note: Don't delete your your chao data or else you will have to do them again.
Sonic Adventure T-Shirt
The following item can be unlocked in Playstation Home. Load a savedata where you have cleared all characters stories to unlock the item.
Super Sonic
Finish the game as Sonic, Tails, Knuckles, Amy, Big and E-102 Gamma. Super Sonic will be avaliable only in Adventure Mode.
Super Sonic
Complete the game with every character.
Trophies
Complete the following tasks to unlock PlayStation 3 trophy rewards.
Trophy
How to unlock
Amy Rose (Bronze)
Become friends with Amy.
Big the Cat (Bronze)
Become friends with Big.
Chao's Best Friend (Silver)
Get all Emblems of the Chao Race.
E-102 'y' (Bronze)
Become friends with E-102.
Knuckles the Echidna (Bronze)
Become friends with Knuckles.
Metal Sonic (Bronze)
Get all 130 Emblems by playing Sonic Adventure DX.
Metal Sonic Master (Silver)
Get Level A on all the Action Stages by using Metal Sonic.
