This glitch works for Knuckles, Tails, and Cream. Go to a Boss with one of those characters and fly or glide to the left side of the screen. They will be blurry and you will see doubles of them. Also, if you are Cream and she gets tired while flying, when Cheese tries to pull her up there will be two Cheeses.
Bonus level
Successfully complete the game with all seven Chaos Emeralds with Amy, Cream, Knuckles, Sonic, and Tails to unlock a new level at the end of Sonic's map screen.
Boss option in time attack mode
Successfully complete the game with all seven Chaos Emeralds with any three characters to unlock the "Boss" option in time attack mode.
Cheese gets rings
When playing as Cream the Rabbit, you can use Cheese (her Chao) for more than attacking enemies. You can also call Cheese to snag Special Rings.
Defeating Tails' final Boss
On the huge machine at the end of the final level, use Tails' propellers to hit his head. Note: You need to hit him with the propellers precisely.
Go higher and farther off a red ramp
When you get to a red ramp in the level 1, you can get farther and higher. When your about to jump on it, press A when about to jump. This only can be done on level 1.
In-game reset
While playing a game, press Start + Select + A + B.
Penguin Slide
Heres how to do a penguin slide. First make sure that your facing a boss as Knuckles.(The first boss is usually the best one to fight for this code) Glide and hold the A button,as you slowly reach the floor. When you get to the edge of the left part of the screen while holding A you will be doing a penguin-like slide.(Note) Release A to stop sliding.
Play as Amy
Successfully complete the game with all seven Chaos Emeralds as Cream, Knuckles, Sonic, and Tails to unlock Amy.
Play as Cream
Successfully complete the Leaf Forest level with Sonic to unlock Cream. Cream is extremely useful when facing Bosses because her Chao will attack it when you press B button. This makes it especially easy to defeat Bosses that are hard to hit, such as the fourth, sixth, and eighth.
Play as Knuckles
Successfully complete the Sky Canyon level with Sonic to unlock Knuckles.
Play as Tails
Successfully complete the Music Plant level with Sonic to unlock Tails.
Sound test
Successfully complete the game with all seven Chaos Emeralds with any two characters to unlock sound test. Note: For more sounds, successfully complete the Extra Zone with Sonic.
Speed boost
At the start of any non-Boss level, you can get an extra boost of speed out of the start gate. Quickly hold Right just before the counter says "START!". This may require a few attempts to get the correct timing. Also, use the following for a speed boost on Sky Canon. Choose any character that is fast. Select the Sky Canon Act 2 stage. Once you find a fan that blows you to get more speed, go back near the fan. Wait a few seconds and their speed will increase. After this process, turn around. This is useful with Tails because he starts by walking, then jogging, and finally flying.
Tiny Chao Garden
Successfully complete the game with all seven Chaos Emeralds with any character to unlock Tiny Chao Garden.
Unlock Characters
Cream- Finish Leaf Forest as Sonic.
Knuckles- Finish the Sky Canyon level as Sonic.
