Super Dragon is the name of Yoshi's Final Smash, which he uses in Super Smash Bros. Brawl. When Yoshi collects the Smash Ball, he will start glowing. He will then sprout wings, and gain the ability to breath fire. This allows Yoshi to spit out Fireballs and breath a ray of flames, which can devastate opponents. On top of this, Yoshi will also have the ability to fly, allowing him to hover above ledges without falling in. However, the effects last only a small while, and Yoshi will eventually lose his wings and fire powers, which will be bad if he is hovering over an edge. The attack is named after Yoshi's nickname in Super Mario World, the Super Dragon Yoshi, and the effects are based on Yoshi's abilities when he eats a Red Shell (Fire Power) or Blue Shell (Flying Power), which is also in Super Mario World.
After a short while, Yoshi's amazing ability and his wings will vanish. Surprised, Yoshi will look back to where his wings once were, only to see that they're no longer there. It's suggested that during the conclusion of Yoshi's final smash, you stay in the middle of the stage, because otherwise, you'll fall to your death when he loses his wings if you're too far out.
"Yoshi with wings on his back that give him the power to fly freely across the sky. In this state, he can spew giant fireballs. He is more mobile and powerful, but the inertia makes movement quirky, so it takes some skill to master flight. Yoshi returns to a normal state after a set period of time has passed."