From the Super Mario Wiki
Lamb's Lure is an attack Item from the game Super Mario RPG: Legend of the Seven Stars. This item is obtained after using the Mystery Egg 10 times. When used, a sheep appears on the screen and turns an enemy into a sheep itself. Then, both sheep fly past the top of the screen. This item cannot be used on Bosses or other large enemies. When Lamb's Lure is used forty-eight times, it will become a Sheep Attack.