*Rebecca is a yellow tender engine who lives and works on the Island of Sodor and is the North Western Railway's number 22 engine.

Despite her large size, Rebecca is shy and sometimes clumsy, but not afraid to stand up for herself and is not intimidated by the older engines. At times, she feels the need to be on the same level as the other engines, which can make her anxious or overhasty. But despite her insecurities, Rebecca loves to see the best in everyone and all her friends appreciate her kindness and enthusiasm. She also has the uncanny ability to work with Troublesome Trucks without trouble on the first try, something that confuses even the trucks themselves. Because Rebecca is so willing to see the good in others, she can occasionally be gullible (as shown when she fell for one of Diesel's tricks) but she is also very honest, willing to tell the truth if needed. Rebecca has a big heart and is usually happy-go-lucky and cheerful. Unlike Gordon at times, Rebecca acts very humbly whenever she causes a mishap.

Rebecca is based on a Southern Railway (SR) "West Country" and "Battle of Britain" class (also known as "Light Pacifics"), a class of 4-6-2 tender locomotives designed by Oliver Bulleid and built between 1945 and 1951. These engines were classified as mixed-traffic locomotives when introduced and used for a wide variety of passenger and goods trains, including famous expresses such as the 'Golden Arrow' and the 'Atlantic Coast Express'. The "West Country" and "Battle of Britain" class engines were smaller and lighter versions of Bulleid's earlier "Merchant Navy" class, originally built with 'air-smoothed' casing, chain-driven valve gear and tenders with tall streamlined sides. Ten un-rebuilt members of the class have been preserved, one of them, Blackmoor Vale on the Bluebell Railway and another, Winston Churchill at the National Railway Museum. Another preserved member of the class, Swanage, appeared in Thomas and the U.K. Trip when the Ponkickies characters, Gachapin and Mukku were visiting several heritage railways.

While Rebecca is modelled on the un-rebuilt version of the locomotive, her tender design resembles the cut-down version used by rebuilt and un-rebuilt members of the class in British Railways service. Additionally, she features several differences over her real-life basis, including an altered front end with a larger and lower buffer beam, driving wheels which share the same design as Hiro and plain disc wheels for her front bogie, trailing truck and tender, as opposed to the Bulleid Firth Brown disc wheels found on her prototype. Rebecca's cylinders and cab roof also have a significantly different shape compared to those on the real "Light Pacifics".

Rebecca is painted sunshine yellow and bluish black with white lining. Her wheel rims are painted white, her front end is painted red and she has red and orange stripes painted along her sides. Rebecca also has two blue nameplates on her smoke deflectors with her name painted on them in white. Her number (22) is painted on the sides of her cab in white and the initials "N.W.R." are painted on the sides of her tender, also in white.*