Super Sonic

Super Sonic is a special form that Sonic takes on after collecting the seven Chaos Emeralds. His super form grants him increased speed, the power of flight and turns his blue quills upward and golden yellow. Super Sonic is usually invincible to attacks, though he can die by being crushed or falling off screen. Making its debut in Sonic The Hedgehog 2, the form is often attributed to being a nod to the Super Saiyan form from the popular anime Dragon Ball, with the seven Chaos Emeralds also matching the number of Dragon Balls. Since being introduced, Super Sonic has appeared in nearly all the home console games that he has appeared in, with a couple of exceptions, for example being replaced by Darkspine Sonic in Sonic and the Secret Rings. Super Sonic has also recently found his way into the many party games that Sonic has taken part in, for example, Super Smash Bros. Brawl as his Final Smash and Sega Superstars Tennis. In his most recent outings in the main series, Super Sonic is often saved for a special one-off boss fight at the end of the game, unlike his first appearances which allowed you to take control of him during in-game levels. Since "Sonic 3 and Knuckles" Super Sonic has weaved its way into becoming a standard story element for the games; specifically, the final boss stage of many Sonic games onwards would see Sonic(and sometimes some of his friends) gathering all seven Chaos Emeralds and unlocking their combined super-chaotic energies and absorbing them, transforming themselves into meta-powered, nigh-invincible angelic beings, blessed with nearly infinite strength and power and a holy golden aura. Once he(they) gained this form, Sonic and co. would blast and confront Dr. Eggman in one last epic final battle. More often than not, the plotlines would see Sonic use this form and its power to duel with eldritch, god-like, evil entities whom Eggman had unleashed upon the world as a part of his plans(which had failed due to Sonic's interventions) and now posed much greater threats than the Doctor himself, and Super Sonic had take them down. Perfect Chaos, Dark Gaia, and Solaris are all great examples.

Sonic the Hedgehog 2
This was Super Sonic's first appearance. His design resembled Sonic's, only with yellow fur and upturned spikes.

Sonic the Hedgehog 3
Super Sonic's design remained unchanged from Sonic the Hedgehog 2, only he had green eyes instead of black. From Sonic the Hedgehog 3 and onward, Super Sonic would play a much more significant role in the games, usually appearing in the ending.

Sonic the Fighters
Super Sonic could be unlocked after beating the game with all seven Chaos Emeralds.

Sonic R
After finding the seven Chaos Emeralds on the race courses, Super Sonic can be unlocked. He has a very high speed and acceleration, but cannot corner easily.