From the Super Mario Wiki
“And for Sleepy Sheep?”
—Arfur, Paper Mario: The Thousand-Year Door
Sleepy Sheep is an item found in the Paper Mario series. When used, many sheep run across the screen, causing most enemies to fall into a deep slumber, in which they cannot perform any moves until they awaken. Some enemies have a higher resistance to sleep than others - so it is never guaranteed that this item will affect all enemies in a battle. Bosses have a very high resistance to sleep and many other status conditions.
In Paper Mario: The Thousand-Year Door, if Zess T. mixes a Point Swap and a Tasty Tonic, a Sleepy Sheep is produced.
In Super Paper Mario, Sleepy Sheeps can be bought from shopkeepers, and sometimes dropped by enemies. If given to Saffron, she will cook up a Mistake (second type)
In Paper Mario: Sticker Star, there is a hammer sticker called the Baahammer. It's a purple hammer with a Sleepy Sheep symbol on the top. Any undefeated enemies after using the sticker in battle will end up falling asleep, making them lose a turn.
Names in Other Languages
||cute variation of "sheep"