The Scottish Twins

The pair of twins that arrived from the Island of Sodor to help the Fat Troll.

Original ordering mistake
When the Fat Controller ordered them from the manufacturers, he accidentally wrote "7" in the quantity box instead of "2", which resulted in four Donalds and three Douglases arriving on the Island of Sodor. The extra Donalds and Douglases were returned for a full refund, but not before they had their wicked way with Thomas.