- "Ballast is, by far, the most ridiculous art form I've ever heard of."
- ―Percy insulting Doc, Pummeling Percy
Doc is a yellow Ballast Spreader that helps keep all of Sodor's trackbed in good condition. He believes his ballast work is an art form of its own.
Doc was brought to Sodor to help spread ballast on the line. He resides close to the Small Railway Engines by the Arlesdale Railway.
He was helping to refurbish the line close to a refinery when Percy was very rude to him.Donald and Douglas later came to his defence.
Doc has a very artistic personality and always strives for utopian work. He can be very temperamental if he feels that any engine denegrates or undermines his work. He can often rant and rave about the sheer perfection of his ballast, which can get very boring. He is also prone to "introspective phases" where he is pensive and sad and does not talk to anyone for almost a month.
- Season 1: Lift Bridge (cameo), Dodge (original version only, cameo), Stepney Makes an Entrance, Rising to the Occasion (cameo), Snow Blind (mentioned), Buffer Bashing (cameo), Cannon Fodder (cameo), Conspiracy Theory (cameo)
- Season 2: Paxton and Norman (cameo), Rosie (cameo), Rock-Star (cameo), Pummeling Percy, Tag-Team (cameo), Swashbuckler (cameo)