Donald and Douglas are twin Scottish engines.
Appearences[]
- Season 1 - Gordon Proves his Point (Douglas only), Crossed Lines (Donald only; Douglas does not speak), High-Speed Gordon (Donald only; Douglas cameo), Old Stuck Up (Douglas does not speak; Donald cameo), and Fire Engine (Donald only)
- Season 2 - The Missing Coach (Douglas only; Donald does not speak), Scrambled Eggs (mentioned in deleted scene), andGordon Goes Foreign (Douglas only; cameo)
- Season 3 -Breakvan, Domeless Engines (cameo), Hullo Twins, and The Runaway (mentioned)
- Season 4 - The Deputation, Light Work (Donald only; Douglas cameo), Diesel's Big Idea (Donald only; Douglas does not speak), and Winter Mischeif (Donald only; Douglas does not speak)
- Season 5 - Rusty to the Rescue (Douglas only), Henry Sees Red (Donald does not speak; Douglas cameo), Out of Puff, Escape (Douglas only), Little Western , and Stepney's Special (Douglas only)
- Season 6 - Bright Spark (mentioned), Ballast, Resource and Sagacity, Donald's Duck (Donald only; Douglas does not speak)
- Season 7 - Mountain Engine and Percy's Porridge (do not speak)
- Season 8 - Edward's Exploit, Determination, and Toad Stands By (Douglas only)
- Season 9 - Limits
- Season 10 - Tenders For Henry (Donald only), The Fat Controller's Engines (cameos), Thomas Comes to Breakfast, Bowled Out, and Train Stops Play (Donald only; cameo)
- Season 11 - Paint Pots and Queens (Donald only; cameo)
- Season 12 - Super Rescue (Donald only; does not speak), Bear and Old Dean Morris (Douglas only)
- Season 13 - The Engines and The Three Horrid Lorries (Donald only; does not speak), and Bulgy (episode) (Donald only; does not speak)
- Season 15 - Buffer Bashing
- Season 16 - Golden Jubilee
- Season 17 - Make Someone Happy (Donald only; cameo), and Thomas and the Missing Christmas Tree
- Season 18 - Bluebells of England (Douglas only), Twins Falling Apart, and The Red Balloon
- Season 19 - Harvey To the Rescue (Douglas only; cameo)
- Season 21 - Thomas and Elizabeth (Donald only; cameo)
- Season 26 - Gordon and the Engineer
- Season 28 - The Spiteful Brakevan's Revenge