|Position||6th Skarloey Railway Engine|
|Age||83 (as of 2011)|
Duncan is the sixth narrow-gauge engine on the Skarloey Railway. He speaks with a Scottish accent.
Duncan was derailed by his train of slate trucks at a bend after he gave them a bump for insulting him with his rock 'n' roll song which was playing at one of the stations. He felt upset that Peter Sam came early and argued with him at the sheds as Duke tried to intervene saying that Peter Sam is a hard worker and used to be called Stuart, a Railway Series reference to Granpuff. When Duncan broke his right cylinder while pulling a passenger train on the hill, Peter Sam who came in with a supply train to the slate mines helped getting him up on the hill. At the next station, the Scottish engine apologized to Peter Sam and Rheneas took him all the way to get the passengers safely home.
He later commented to Sir Handel why the railway would need Rusty. The little diesel had overheard the conversation and was angry about it. Sir Handel chuffed off after the Scottish engine finished his talking at the station. The engines later said about both Sir Handel and Duncan's comments before The Thin Controller came to see the engines about building a new engine under Mr. Hugh's management and Rheneas' overhaul is nearly completed in full timing.
In 2009, Duncan was admired by the sound of George Carlin, an American comedian who died in June 2008 at the age of seventy-one. The Scottish tank engine liked hearing the comedian and even laughed at one part involving "blue cheese with some mold in it". In tribute to Carlin, Duncan chose his TV series livery of yellow which stunned the other engines. Skarloey was in shock, Ivo Hugh said it was rather brave and Duke said if the livery is going to be a permanent change to the Scottish tank engine. Duncan kept his color in the ninth episode, Duty of Care and had a cameo appearance in it.
Duncan is based on Douglas, the #6 engine on the Talyllyn Railway. He was built in 1928 and arrived on Sodor 30 years later.
- Season 4 - Hard Work and Post & Prejudice (cameo)
- Barry the Rescue Engine - The Lucky Ones (cameo), Testing Times (cameo) and Back on Track (mentioned)
- Season 5 - One of a Kind
- Season 1 STMY - Ode to George Carlin and Duty of Care (cameo)
- Season 2 STMY - Last Straw (cameo), Confidence
- Duncan has received a new model for the second half of Season 2 STMY along with the rest of the Skarloey Railway fleet.