This is Number 6
Duncan is a yellow narrow gauge tank engine. He is named after the Arlesdale Railway's controller, Mr. Fergus Duncan. He is good friends with Sir Handel, has a twin at the Talyllyn Railway named Douglas and is known to "rock 'n' roll".
Duncan is a yellow narrow gauge tank engine that works on the Skarloey Railway,he had many adventures like pushing Rickety up the Quarry Mine Tunnel,shunting trucks into a goods train and taking them up Gordon's hill. We first met him in Home at Last, which is not one of the Thomas The Tank Engine and Friends Wooden Railway Adventures, but we also met him in some wooden adventures.
- Season 1: The Trouble With Trucks (does not speak) and Wilbert, Frank, and the Milk (cameo)
- Season 2: Skarloey & Rheneas Depart For Crewe
- Season 3: Rusty Rocks the Railway, Clumsy Culdee and Rickety's Revenge
- Season 4: Duncan and the Passengers
- Season 5: Skarloey and the Big Hill
- Season 6: Little Engines, Big Help
- Season 7: Neil's Nonsense and Not So Fearless Freddie
- Season 8: The Crash Course and Find That Bike!
- Season 9: A Frenzy for Falcon and Special Tunnel
- Season 10: A Crack in the Track and Tour de Sodor
- Season 11: Around the Railyard in 64 Seconds, Duncan in the Dumps, Hank and the Hatt St Crossing (cameo), Wooden Brakes (cameo), and BoCo and the Cocoa (cameo)
- Season 12: The Importance of Being Billy (cameo), Gordon's Last Hurrah (cameo) and Rheneas and the Risky Rendezvous
- Season 13: Victor's Loco Motives (cameo) and Ivo Hugh's Day at the Zoo (cameo)
- Season 14: Millie's Castle Hassle and Freddie at the Ready
- Season 15: Philip Finds a Friend (cameo) and The Maron Station Makeover (cameo)
- Season 16: Bulstrode Barges In (cameo), Luke Dukes It Out and Bowler Strikes Again (cameo)
- Season 17: Hard to Handel (cameo)
- Lady the Lost Engine (does not speak)
- Since to Duncan's rock 'n' roll, he sometimes derails on bumpy lines.
- Duncan is the only Skarloey Railway engine which ThomasWoodenRailway didn't change over to his newer model.