Yoshi Egg

From Mario Kart Racing Wiki

In Mario Kart 64, a giant Yoshi Egg appears as an obstacle in Yoshi Valley. In Mario Kart: Double Dash!!, the egg is used to hit your enemies in front of you. It then releases many items like a Mushroom, a Green Shell, a Bob-omb, a Red Shell, a Star or others . If the egg does not hit an opponent or structure it will break shortly after toss. Only Yoshi uses this power-up in Birdo can also use this although Birdo's is pink. It is called a Birdo Egg.