Go to the Mystic Ruins and go to the ditch with the waterfall, then find the stone jut hit it and a chao egg will fall out of the waterfall it can't be picked up until it is at the shore and there you have a new Chao friend.
Chao flying
To help your chao fly, give it a bird.
Chao Running
To help your chao run, give it a deer animal, a rabbit or a wallaby.
Chao strength
To increase your chao's strength, give it any of the following animals: elephant, gorilla, lion.
Chao swimming
To improve your chao's swimming ability, give it any of the following animals: seal, penguin, beaver.
Chop a chao
Go into adventure mode and pick e102y (i will call him gamma). go to any chao garden, and pick up any chao (make sure its back is toward you). walk toward any body of water, and walk into it. gamma should say "mode change". while hovering over the water, it should look like its getting chopped even though it dosent hurt it. (even more realistic if the chao does not like you)
Extra Chao
To do this cheat, you must have Sonic Advance 1 or 2 and a Gamecube/GBA link cable.Go to the Chao Garden on Sonic DX, and step on the transporter. Then, turn on the Tiny Chao Garden on Gameboy Advance. Transport the chao you have in GBA to the Sonic DX garden. Then on GBA, go to the chao mini-store by pressing L. You will see a free egg. Buy it, hatch it, then transport it to Sonic DX. Keep on doing this until you have enough Chao.
Extra Rare chao egg
Go to the Mystic Ruins then head to the waterfall hit the stone to the right of the ditch, then a rare silver egg will come out of the waterfall, wait till it gets to the shore and take it to your chao garden.
Glitch: Tails in Emerald Coast
As Tails, go to the pool outside the hotel. Go to the right 'till your directly below the balcony. Fly and do NOT move the anolog stick. You'll go through the balcony. Now slowly run outside of the hotel to a small platform. Note:This next part can be easier with the jet anklet. Now,try to fly over to the beach far enough so you won't die, and go to the blue gate. And you're in Emerald Coast. Note:You can only play the first part,then you'll back to the pool.
Glitch:Sonic Fall Though Ice Mountain
To do this glitch when sonic makes it down the ice mountain try to go back up and then when your all the way up you'll fall in a hole and keep falling for 3-6 seconds and then die.
Glowing Pinball
When your in the casino as Sonic, roll up until he starts to glow and hold the button down. Then walk into one of the pinball entrances while holding down the B or X button then hold it down until you start playing pinball and the ball should glow.
Gold Chao
Go to the police station and pick up the egg-shape rock behind the wall. Then go to the antique shop in station square. Replace the egg with the rock a there you go! (all in SS)
Gold egg
Go to the city area then you go to the store across from the restaurant you will see a gold egg take the stone that is shaped like an egg by the palm trees. Then go to the store put the stone down, pick the gold egg up then switch the stone with the egg. Then finally go to the chao garden with the gold egg. And there you go.
Imprison a chao
Choose any character and go to the chao garden. Pick up a chao and go to the red or green door. Get close enough to open the door but don't enter. Move just enough to get the throw option and chuck that thing in there! Your chao will be I too deep to get out. (if you leave, it will be released).
Infinite gold and silver chao
Make an account with the Chao garden in slot 1. pt the gold and silver Chao in there. Now create an account in slot 2. Put their gold and silver Chao in the Chao garden. (you will have it unlocked, it will be the same one) then delete slot 2. repeat as perferred.
In-game reset
Hold Start + A + B + X for a few seconds during game play.
Light speed trick
Go to Twinkle Park and kill all the guys in the bumper cars and then use the light speed thing and get in the bumper car and if you let go of the B button Sonic should be glowing.
Mission mode
Successfully complete the game in adventure mode with all characters to unlock the "Mission Mode" option at the main menu.
Play As Metal Sonic
Collect all 130 Emblems to unlock Metal Sonic in trail mode.
Play as Super Sonic
Complete the game using all six starting characters to unlock Super Sonic. Sonic will transform into Super Sonic after some time into the next game.
Play as Tails
Controller two may be used for Tails after he is obtained during game play in story mode. Note: Shields, invincibility and extra life boxes have no effect on Tails if collected. Note: If Tails goes too far away from Sonic, he will appear next to Sonic.
Shake a chao
Select sonic and make sure you can perform the light speed dash. Go to the chao garden and charge up (this is quicker if you have sonic's braclet). DO NOT LET GO OF B!!!!!!!!! while your glowing blue, walk up to a chao and press X while still holding B to pick it up. Move the control stick any direction to shake the chao.
Silver chao
Go to mystic ruins and jump in he pit. On the wall by the stairs should be a platform thingy. Run into it and it should be in the water. You'll have to wait till it gets to the land to pick it up.
Sonic Chaos: Level select
Press Up(4), Right, Left, Right, Left, Start when "Press Start" appears at the Sonic Chaos title screen.
Sonic Labyrinth: Level select
Press Up(2), Right(3), Down(6), Left(9) when "Press Start Button" appears at the Sonic Labyrinth title screen.
Sonic Spinball: Disable gravity
Enter the "Sound Test" option for Sonic Spinball. Then, play the following songs in order: 0, 9, 0, 1, 6, 8.
Sonic Spinball: Faster background music
Enter the "Sound Test" option for Sonic Spinball. Then, play the following songs in order: 0, 4, 2, 5, 5, 7.
Sonic Spinball: Level select
Enter the "Sound Test" option for Sonic Spinball. Then, play the following songs in order: 0, 2, 1, 5, 6, 6.
Sonic Spinball: Zoomed in view
Enter the "Sound Test" option for Sonic Spinball. Then, play the following songs in order: 0, 2, 1, 1, 6, 6.
Sonic The Hedgehog 2: Level select
At the Sonic The Hedgehog 2 title screen, Tails will blink his eyes (first once, then two times quickly). While holding Down/Left + A + B, tap Start just when his eye shuts on the second blink of the double-blink.
Toggle Game Gear game screen
To view the Game Gear games in a smaller, not pixelated view, press L + R. Pressing L + R again will return the view back to normal.
Two player Game Gear mode
Press Start on controller two to display a second Game Gear screen for that player. If the original Game Gear game supported the multi-player link, the current game will switch to multi-player not. If the game did not support the multi-player link, game play on each screen will be unrelated.
Unlock GameGear Games
Get a Sonic emblem or finish ten missions. The 'minigame' option will be added to the main menu.