Stanley is a silver tank engine.
Stanley was brought to Sodor to take care of Thomas' workload during the restoration of Great Waterton. Upon his arrival, Stanley became very popular and enjoyed the company of the engines. Stanley's popularity caused Thomas to feel jealous and later neglected. Thomas felt that Stanley was newer, bigger, and stronger than he - and would take over his place on the railway. Thomas then planned to make Stanley look weak - the trick backfired and caused Thomas' friends to consider him mean and incompetent. When Thomas later went missing, Stanley was the first to realise Thomas' feelings. He searched for Thomas until he finally managed to find and rescue him. Then, both became friends and with a combined effort made it back to Great Waterton in time to prepare for the opening celebrations. Stanley later worked in the yards with Thomas and James during the winter and helped with the rebuilding of the Sodor River Bridge. Also, he went to Great Waterton with Gordon to pick up passengers. Stanley was amongst the engines at Knapford who were worried about Percy's whereabouts when Percy was spending his time with the Diesels at the Dieselworks. Later on in the winter, he suffered from a faulty firebox and Thomas came to his aid once again. In more recent seasons, Stanley can be seen working at the Shunting Yards, the China Clay Works and Ffarquhar Quarry. Salty also mentioned that Stanley, in one of his spooky stories, was an old engine who lost his flatbeds while climbing a hill, and ever since then his flatbeds haunt the rails. In Sodor's Legend of the Lost Treasure, he helped with the construction of the Harwick Branch Line. He was the first engine to cross the unstable track that the Pirate Ship was under.
Stanley is the "boy-next-door" of the Fat Controller's Railway. Cocky, cool, and cheery, he is a little bit bigger, a little bit newer, and a little bit stronger than Thomas, which, at first, made Thomas jealous when all focus seemed to be on this shiny, new arrival, especially when he began helping with the restoration of Great Waterton. However, even Thomas was soon won over by Stanley's positive attitude, charm, and friendliness and came to see why he was so popular and well-liked among the other engines. As such, Thomas and Stanley are now firm friends. There is nothing Stanley would not do for another engine. And if he could not do it, he would find someone who could. He is sleek, smart, and stylish and his silver and light grey appearance, with striking red wheels and a shining smoke box certainly makes him look the part as he eagerly goes about his work.
Stanley is a hybrid cross of a Hudswell Clarke 0-6-0ST engine and Kitson's No. 5459 "Austin I", but with a taller funnel.
Stanley is painted in a white livery with a metallic silver smoke box, red wheels and lining. He has a red running plate with a dark grey basecoat, and his name on each side of his saddletank.
- Matt Wilkinson (UK; fifteenth season onwards - excluding nineteenth season)
- Ben Small (US; fifteenth season - eighteenth season)
- David Menkin (US; Samson at Your Service only)
- Rob Rackstraw (UK; nineteenth season only - US; nineteenth season onwards)
- Hiroshi Tsuchida (Japan)
- Benjamin Morik (Germany; fifteenth season onwards)
- Christoffer Staib (Norway; fifteenth season only)
- Stig Krogstad (Norway; Day of the Diesels onwards)
- Adrian Perdjon (Poland; fifteenth season and Day of the Diesels)
- Piotr Warszawski (Poland; eighteenth season onwards)
- José Luis Rivera (Latin America; Day of the Diesels onwards)
- Mercedes Espinosa (Spain; Day of the Diesels onwards)
- Anton Savenkov (Russia; Samson at Your Service onwards)
- One of Stanley's models used to be on display in Canada at Nitrogen Studios.
- Stanley's popularity with the public has grown following an online video called "A Toy Train in Space", in which a Wooden Railway model of him was sent into space. As a result, both a Take-n-Play and a Collectible Railway "Stanley in Space" have been released.
- Stanley's smokebox is silver. However in real life, UK locomotives had their smokebox painted in black.
- Stanley's whistle sound is Thomas' at a lower pitch.
- Stanley's TrackMaster model features wheel arches.
- Stanley has had several modifications throughout the television series. These include:
- Season 14:
- His smokebox became shorter in height.
- Season 19:
- He gains a brakepipe.
- He received permanent head and tail lamps.
- He gains a lamp-iron.
- He received front and rear brake-pipe outlets.
- Season 14: