Rollobite

Quote from The Legend of Zelda: The Minish Cap Rollobite figurine:

"Appears in dungeons. His hard shell protects him from swords, but once he rolls into a ball, you can use the Gust Jar to draw him in."

Rollobites are rather helpful enemies as they can be put in holes in order to reach to switches and treasures. Their function is similar to the Magtails of The Wind Waker.