- "Not like Merlin... I am Merlin, the experimental prototype King Arthur class stealth engine!"
- ―Merlin introducing himself, Journey Beyond Sodor
Merlin is an experimental tender engine who believes he has the power to turn invisible.
When Thomas travels to the Mainland, he befriends the experimental engines: Merlin, Theo and Lexi. Merlin sails through life, full of confidence, believing that he has the ability to become invisible. Helping to hide Thomas from Frankie and Hurricane, he promises to help Thomas find his way back to Sodor. Later, Merlin, along with the other experimentals, help Thomas rescue James, who had been trapped in the Steelworks.
Afterwards, Thomas convinces the experimental engines to stay at the Steelworks and help Frankie and Hurricane.
Merlin is full of confidence wherever he goes. He's completely confident that he can turn himself invisible. He's heartwarming, kind, and gentle to anyone he meets. Anytime Theo or Lexi say they can't do anything, he encourages them with, "We can try." He often mispronounces words, such as when he called Sodor "Sonar" and diversion "conversion".
Merlin is based on the LSWR N15 Class, referred to as the "King Arthur" class by the Southern Railway, specifically No. 783 Sir Gillemere. In 1943, Sir Gillemere was fitted with three stovepipe chimneys by Oliver Bulleid as a wartime experiment. The way the smoke was spread out was meant to make the trains less visible to bombers overhead. The experiment was not a success, and the engine was quickly converted back to normal. No. 783 became No. 30783 under British Railways after nationalisation in 1948 and was withdrawn in March 1961.
Merlin's name is likely taken from another King Arthur locomotive, No. 740 Merlin. A single King Arthur is preserved as part of the National Collection, No. 777 Sir Lamiel, and is based at the Great Central Railway, currently awaiting overhaul.
Merlin is painted silver with a red running board and wheels, and black smoke deflectors. He has red and gold nameplates on either sides. His number is also painted white on his front bufferbeam, the sides of his cab and tender.
- Merlin's whistle is an LNER A4 3-chime.
- Merlin's tender is actually a modified version of Bert's.
- Merlin is the second character to have his basis named in the show, with BoCo being the first.
- According to Behind the Scenes: Thomas & Friends: Journey Beyond Sodor, Merlin's facial features were based off of his voice actor, Hugh Bonneville.
- "Invisibility, on!"
- Merlin's catchphrase, Journey Beyond Sodor
- "We can't do anything!"
- "But we can try!"
- Merlin's responding positively to Lexi and Theo, Journey Beyond Sodor
- "Oh, Hurricane! What should I do?!"
Frankie and Merlin, Journey Beyond Sodor
|98462 and 87546 • The Workshop Engines • The Foreign Engines • Diesel • The Foreign Engine • The Derailed Engine • Jinty and Pug • The Diesel • The Scrapyard Engines • D199 • Gordon's Brothers • British Railways Diesels • King James I • Old Stuck-Up • Alfred and Judy • Toby's Brothers • 8783 • 1020 • The Highland Engines • The Diesel Shunter • 31120 • 10751 • Wilbert • Sixteen • Sixteen's Friends • Albert • Bahamas • D5705 • Lemberg • Pretty Polly • The Dukes • British Railways|
|Earnest • Lady • Spencer • Hiro • Hiro's Friends • Connor • Caitlin • Stephen's Competitors • The Mainland Engines • Gator • Samson • Splatter and Dodge • The Mainland Diesels|
|Theo • Lexi • Merlin • Hurricane • Frankie|
|Logan • Sam|
|Ashima • Rajiv • Yong Bao • Vinnie • Carlos • Raul • Shane • Etienne • Frieda • Gina • Axel • Ivan|
|Silver Jubilee • Helena|
|Spencer's Coaches • Connor's Coaches • Caitlin's Coaches • Bradford • Ladle Trucks|
|The Flying Thistle • Thirteen • The High-Speed Post Train|