Egg Roll
Egg Roll is a special move used by Yoshi. It is a smash B move. The executor can steer it by pressing left or right, and stop the attack by pressing B again. In Melee, it can be used to increase Yoshi's horizontal recovery. It is easily countered, but acts as an efficient way to pass an edgeguarder (when Yoshi is off-stage), but if the opponent can reach the egg's height and hit Yoshi it is essentially followed by a death. If preferred, the player controlling the move may wish to hold the B button. This makes it more difficult to control, but allows more damage.
In Brawl, Yoshi's Egg Roll has higher priority. However, Yoshi's air speed is decreased while using the Egg Roll, making it useless as a recovery move. Also, it is notoriously easy to Self-destruct with Egg Roll in Brawl, as Yoshi becomes Helpless if used in midair, and running off platforms with Egg Roll is all too easy.
Origin
The move seems to be unique to the Super Smash Bros. series, but may be based off of Yoshi's Story where upon eating a Turbo Tulip, Yoshi could encase himself into an egg and fling himself at enemies or out-of-reach objects. The Egg Roll would later appear in Mario Power Tennis and Mario Strikers Charged.
The curious thing about this move is its seemingly infinite priority. Other than the space animal guns and some fully charged moves, Yoshi's egg roll essentially cannot be interrupted when Yoshi is at 0%. Characters such as Snake have no defense against this; it even goes through Snake's rockets. If Snake lays a mine using his down smash, the egg will roll over it too quickly for the explosion to affect Yoshi. It is much the same story for other characters, which makes Yoshi able to use this move repeatedly at the beginning of each stock. In addition, Yoshi can pop out of the egg anywhere he wants to, which, with the egg's insane speed, makes it a virtually unpunishable move. As if that's not enough, the move does 10% damage each time it hits and never becomes stale. It has limited knockback, however - it sends the opponent straight above Yoshi - but can still be used to stack damage effectively. In addition, it can shield poke. The bottom line: Yoshi can use this move for an almost indefinite period of time against most characters in the game, and suffer almost no negative repercussions for it.
