*Molly is a powerful, yellow mixed-traffic tender engine who lives on the Island of Sodor and primarily works on the Main Line of the North Western Railway.

Molly is a powerful engine, who is proud of her strength and is happy to put it to use as one of Sodor's bigger engines. She often works pulling empty trucks to the Coaling Plant. Being a sensitive and self-conscious engine, she often worries about fading into the background. Sometimes, taking "empties" (empty trucks/cars) makes her feel less important and sad, but in the end, she will usually see that it is a vital part of operations and an important task after all.

Molly has a peacekeeper attitude, tends to be rather sensible, and is looked upon as a "big sister" by some of the other engines. Because of her sensitivity, she can be easily embarrassed or upset by conflict, and will steam away to avoid it, but she will usually have the courage to do what she thinks is right. Molly likes to be as good as everyone else and wants the other engines to think the best of her.

Molly is based on a Great Eastern Railway (GER) D56 Class "Claud Hamilton", classified as D15 by the London and North Eastern Railway, with a Belpaire firebox, sandboxes on her wheel splashers, and the smaller 'water-cart' tender. Claud Hamiltons under the classes S46/D14, D56/D15, and H88/D16 were built at Stratford Works from 1900 to 1923. Under the LNER, most members of the class were rebuilt into the Gresley designed D16/3 sub-class. Members of this class pulled the Royal Train from Wolverton to the Sandringham Estate for several decades. The last D15 was withdrawn in 1952, while the last rebuilt Claud was withdrawn in 1960. None are preserved, though there were plans to construct a replica of D16/2 No. 8783 before being cancelled in 2024.

Molly is painted bright yellow with red and gold boiler bands, bronze borders around her splashers, sandboxes and tender, and red lining on her tender and around her cab side windows. Her buffer beams, valences and footsteps are all red, while her running board is light grey with yellow trim around the edges. Her cab roof, the lids of her tender toolboxes and the rims of her leading and driving wheels are painted white. Her smokebox and tender wheels are plain black.*