Achievements...
	Amy...
	Big...
	Chao puzzle...
	Clean Pause (any mode)...
	E-102 Gamma...
	Hidden Sonic Adventure Art...
	Knuckles...
	Miles Tails Prower...
	Play Emerald Course in chao ra...
	Super Sonic...
	Super Sonic...

Complete the following achievements to unlock Xbox Live Gamerscore points.

Achievement	How to unlock
Amy Rose ( 10 points )	Become friends with Amy.
Big the Cat ( 10 points )	Become friends with Big.
Chao's Best Friend ( 20 points )	Get all Emblems of the Chao Race.
E-102 ( 10 points )	Become friends with E-102.
Knuckles the Echidna ( 10 points )	Become friends with Knuckles.
Metal Sonic ( 15 points )	Get all 130 Emblems by playing Sonic Adventure DX.
Metal Sonic Master ( 15 points )	Get Level A on all the Action Stages by using Metal Sonic.
Miles "Tails" Prower ( 10 points )	Become friends with Tails.
Mission All Accomplished ( 20 points )	Clear all 60 missions.
Sonic the Hedgehog ( 10 points )	Clear the Sonic story.
Sub Game Master ( 20 points )	Get all Emblems of the Sub Games.
Super Sonic ( 20 points )	Clear all characters stories.
The Adventurer ( 20 points )	Get all Emblems in the Adventure Field.
The Fastest & Strongest ( 20 points )	Get Level A on all the Action Stages.
The Perfect Adventurer ( 40 points )	Get all 130 Emblems.

Talk to her in the Casino as Sonic after finishing Sky Chase.

Defeat Chaos 6 as Sonic.

You must have 3 controllers and the 3rd one must have a memory card for this to work. Start up the game with all 3 controllers plugged in and get into Adventure mode as any character. Now press START on the 3rd controller. Something on the memory card's screen will come up saying "CHAO PUZZLE". Press START again to begin. It is a 3x3 slider puzzle with a random animated Chao doing something for a picture. Use the D-Pad to select the piece you want to move and press A to move it into the open area. You can also move two pieces at once. Press B for a different puzzle. Press START again to quit. There are 15 levels and every 5 you complete there is a congratulatory message from a Chao. After you beat the 15th it will start you at level 1 again.

Pause the game and hold X + Y to clear the game of the pause screen.

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.

You can find some cool hidden Sonic Adventure arts made by SonicTeam themselves by putting the GD-ROM inside the computer's CD-ROM drive. Access the folder inside it and view the .bmp pictures there.

Defeat him after finishing Ice cap as Sonic or Tails.

Finish the C mission of Emerald Coast action stage as Sonic.

Beat the rest of the four courses. Note: Don't delete your your chao data or else you will have to do them again.

Complete the game with every character.

Finish the game as Sonic, Tails, Knuckles, Amy, Big and E-102 Gamma. Super Sonic will be avaliable only in Adventure Mode.