Donald and his brother Douglas are twins. Donald hates to be parted from his brother, and loves to play practical jokes on the other engines. Donald and Douglas love to play practical jokes, especially impersonating one another. They were fitted with nameplates to specifically end this element of their humour.
Donald is the #9 engine. Donald is a 0-6-0 tender engine based on the 812 class built for the Caledonian railway.