The twins were built in St. Rollox Works in 1929 (numbered 57646 & 57647) and worked on the Caledonian Railway in Scotland and had a good service for a few years. Soon in 1959 one of them was bought by The Fat Controller to assist with the workload but he was very surprised to see the twins and there said that they had lose there numbers along there journey so The Fat Controller said that one of them was being truant and find and send him home then ordered the inspector to gave them numbers and set them to work. The two worked hard and until they play a trick after Douglas stunted Thomas' special coach with the others. The Fat Controller told them that there must be no more tricks.
But a brakevan had taken a dislike to Douglas and made his twin Donald angry and after having a talk with him. The van behaved better afterwards until Donald crashed into a signal box and had to have his tender mended James took over the goods work and wasn't to pleased about it. Later Douglas was to bank James' train up Gordon's hill and the brakevan told the trucks to hold back when there were on the hill Douglas pushed too hard and smashed the van too bits Edward came up with the breakdown gang to clear the mess, Edward put in a good word for Douglas and left The Fat Controller thinking about something else.
After a Deputation from the engines for saving Henry and from being sent away The Fat Controller decided to keep Donald and Douglas and they had stayed there ever since.
Later Donald was disgusted what D261 said about the steam engines at the sheds where Duck had told them. Donald was annoyed when George started to brag about how railways are no good.
Donald and Douglas are kind, helpful and very proud of there Scottish heritage. they enjoy working on the railway and are known to be well-behaved. Sometimes they can be charming and quick thinking.