Mystery Egg (Super Mario RPG: Legend of the Seven Stars)
From the Super Mario Wiki
The Mystery Egg is an item in Super Mario RPG: Legend of the Seven Stars. It is obtained from the treasure-hunting Toad in the Moleville item shop for 200 coins. It is initially useless, however, it can be "hatched" into a Lamb's Lure by using it 10 times with Toadstool while equipped with a B'tub Ring. After the tenth time, a sheep hatches from the egg and says, "You're a great shepherd!". If used by someone other than Toadstool, the item only buzzes.
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