Bill and Ben are tank engine twins belonging to the Sodor China Clay Company. They are young and cheeky and love playing jokes on the bigger engines, but Edward and BoCo are known to discipline them. They work in the china clay works and at Brendam Docks, where they shunt trucks. In Thomas & Friends, they briefly worked at Ffarquhar Quarry, where the task of keeping them in order fell to Mavis.