They work at Pleasure Island. Their job is to help the Coachman sell donkeys. They were told by the Coachman saying "Come on. Let's have another". They always shut the doors and lock them tight. They put donkeys inside the crates and take them to the city by boat.
They are common enemies in the fifth stage of the SNES video game, Pinocchio. Here, if Pinocchio attacks them when their back is turned, they dissipate in the air; another hint that they are shadow creatures.