|First Appearance||Culdee Crosses the Border (cameo)|
|Basis||BR Class 08 diesel shunter|
|Livery||Blue with yellow lining, yellow hazard stripes, and red wheels|
|Voice Actor|| SR3DFilms
Sidney originally worked on an old, run-down railway with Bear, Norman, Dennis, Rusty, and Paxton. He was quite often drawn into Norman's schemes due to his forgetfulness and gullibility. Once the railway went out of business, the six engines were bought by Sir Topham Hatt, and their controller was also brought to Sodor to work as a stationmaster.
Once Sidney arrived, he caused havoc, due to him constantly forgetting his jobs. He was sent to work at the Ffarquhar Quarry with Mavis, but he kept forgetting his orders and causing accidents. He did, however, prove his worth when he saved Fergus from a potentially terrible accident, which was caused by Max and Monty's recklessness. Now, he is well respected by all the engines, despite his forgetfulness.
Sidney was spotted helping out with the Narrow Gauge Expansion Project. He also helps out with the rebuilding of Ulfstead Castle from time to time, but mostly works odd jobs on the main line.
Sidney is kind, well-meaning, and patient. However, he is extremely forgetful, which can cause him to be difficult to work with, and can cause others to become very frustrated with him. Sidney can be so forgetful that someone can introduce themselves to him, and he can go to shunt some trucks, come back, and ask that same engine what their name is. He can also start off his day somewhere and end up somewhere else, not remembering his entire day, or even what his name is.