Super Sonic

Super Sonic is a form Sonic the Hedgehog takes after obtaining all 7 Chaos Emeralds. This power appears in Super Smash Bros. Brawl as Sonic's Final Smash.

When Sonic transforms, after saying "Now, I'll show you!", he gains the ability to fly around the stage at an incredible speed. The transformation lasts for about 15 seconds, and, while Sonic is transformed, he is completely invincible. Sonic can attack in this form by simply ramming into opponents; the faster it's going, the more damage is dealt. It is similar in function to Pikachu's Final Smash, Volt Tackle, except that it cannot go through platforms like Volt Tackle can, and has knockback and better control unlike, and superior to, Volt Tackle. Super Sonic can't KO himself when he reaches the edge of the screen, regardless of how far it is going, but if he turns back to normal while he's too far away to recover, he'll be penalized with a self destruct. If it is used when the section of the Bridge of Eldin is materializing the move will end instantly. This is also useful when Sonic is falling down from the platform. This prevents it from being KO'd as it can break his fall. Also, if it has stopped or is going too slow, it can't even go through a fall-through platform.

Trophy Description
''Sonic's Final Smash. The Chaos Emeralds give energy to all living things, and Sonic's gathered all seven of them, then used their power to transform into Super Sonic. His abilities in this form far surpass his normal ones, and he is even able to fly. He uses a lot of energy in this form, so he can only remain in it for a short time.''

Chaos Emeralds
Chaos Emeralds are a recurring feature in Sonic the Hedgehog series. In the final smash, the Chaos Emeralds can be seen briefly before Sonic turns into Super Sonic, and once he transforms back into Sonic. In the latter instance, the Chaos Emeralds fly off the screen, in 2-D.

Overview
In the games, Sonic had to collect all 7 (6 in the first game therefor he could not transform) Chaos Emeralds in order for him to turn into Super Sonic. In the older games, the Chaos Emeralds were hidden in Special Stages. In the recent Sonic games (more specifically, the 3D games), Chaos Emeralds were required to progress through storylines in the games.

In Super Smash Bros. Brawl
When Sonic activates his Final Smash, Sonic uses the Chaos Emeralds to transform into Super Sonic. The emeralds can be seen briefly before he turns into Super Sonic.

Trivia

 * In Sonic the Hedgehog 3, its eyes were green. It was later changed to red when Sonic's new look had green eyes in his normal form.
 * The Final Smash's trophy states Super Sonic first appeared in Sonic the Hedgehog 2 and Super Smash Bros. Brawl, which means that it is one of the few Final Smashes that weren't created for Brawl (others include:  Giga Bowser, Beast Ganon, Wario-Man, Light Arrow, Landmaster, Cook Kirby, Volt Tackle and PK Starstorm)
 * It's worth noting that the Final Smash Trophy depicts Super Sonic with all head quills standing up. The only exceptions in the Sonic series were Sonic Adventure, Sonic Adventure 2, and the Sonic Advance series. From Sonic Heroes onward, the raised quills return. When Sonic begins flying, his quills take the slanted angle that was depicted in the Sonic Adventure and Advance series. When he stops, his quills return to the raised position.
 * While Sonic is still Super Sonic, it is impossible for Sonic to be KO'd in any way.