In Day of the Diesels, Dart complains about needing a new crane and hides Flynn's hose in the rubbish by order of Diesel 10.
He then helped Thomas fix Ol' Wheezy and later fixed Gordon's bufferbeam.
Dart works at the Vicarstown Dieselworks to support and assist Den. Den and Dart have worked together for so long that Dart can often guess what Den is thinking before he can get it out himself. Although not so much the thinker of the duo, he is usually the doer and can be the chattier of the two. He quickly buzzes about the Dieselworks, occasionally bashing, crashing, and clanging into things. He can be heard to grumble "Dizzy Diesels!" when something goes wrong. Dart is very able in his work and a valuable team player. Despite being small in size, he is feisty and fast. Dart also like jokes, sometimes to the annoyance of the other Diesels. If feeling bothered, particularly by the steam engines, Dart is far from devious, but can get grumpy, gruff, irritable, and sometimes cheeky too, but otherwise he is the quick-witted assistant of the Dieselworks.
Dart is a 4w Diesel-hydraulic shunter built by W. G. Bagnall.
Dart is painted yellow and red with white lining and the Dieselworks logo on the sides of his cab.
- Rupert Degas (UK/US; Day of the Diesels - sixteenth season)
- Steven Kynman (UK/US; seventeenth season onwards)
- Kunihiro Kawamoto (Japan)
- Christian Greger Strøm (Norway; fifteenth season only)
- Stig Krogstad (Norway; Day of the Diesels onwards)
- Lennardt Krüger (Germany)
- Jan Kulczycki (Poland)
- Though he is always with Den, in The Missing Christmas Decorations he is seen without him.