Rusty is a trusty, tame, friendly little Diesel. He is a dedicated worker, often maintaining the line, while understanding and respecting the importance of his duties. He also has a rather distinctive two-tone horn. Rusty is quick to remind others with regards to proper conduct, particularly Duncan, who was initially very suspicious of the little Diesel. He has a good working relationship with both Skarloey and Peter Sam in particular. Caring, calm, and quick-thinking, Rusty is modestly a credit to the Skarloey Railway.
Rusty is based on the Talyllyn Railway's Midlander, a Ruston Hornsby diesel, Unlike his basis, Rusty was never fitted with a different shaped radiator.