Part of the Thomas Wooden Railway System by Learning Curve The people on the Island of Sodor need milk, and they can always count on the Sodor Dairy Cars to deliver it. The children especially love to see the Dairy Cars and hear the cows moo as they pass by. This new and exciting addition to the Thomas line plays a moo sound when a little engineer slides the side door open to see the cow. Includes milk cargo car with removable milk barrel. Two button cell batteries required included.