Yellow Shells are yellow Koopa Troopa shells found only in Super Mario World. When Yoshi hits the ground after a jump, with a Yellow Shell in his mouth, a shockwave will surround him. This will cause the enemies to flip over or defeating all nearby grounded enemies. Yoshis can also spit it back out, in which case it will behave like a Green Shell does, flying out at high speed and knocking over all enemies in its way.
Like other Koopa Troopa shells, the Yellow Shell will be launched when the Koopa Troopa wearing it is jumped on. It can also be held and thrown.