Bo Peep's Sheep are three porcelain sheep joined together and sometimes mistakenly believed to be a single sheep with three heads who appear in Toy Story and Toy Story 2 as minor characters. They enjoy causing mischief, such as pulling the video game remote from Rex in Toy Story 2. When they cause mischief, they can only be stopped by their shepherdess, Bo Peep. At the end of Toy Story, the sheep are seen above Woody and Bo Peep, with a branch of mistletoe. The sheep do not appear in Toy Story 3, having presumably been sold in a yard sale, or donated with Bo.
It is very likely that the sheep will reappear in Toy Story 4, as Bo Peep will be returning as well.