Den is an intelligent diesel shunter that shunts trucks at Vicarstown Yards.
Den was purchased many years ago and was concealed in Vicarstown with his partner, Dart. The two diesels are as close as brothers and even finish each others sentences. The two do odd jobs and are located at Vicarstown. They have also done some shunting work for the Ministry of Defense. Recently however, the pair has also been loaned to Walter Sliggs at the Kellsthorpe Refinery.
Den and Dart were sent to work at High Peak Marshaling Yard when Hank was taken out of service due to an accident he had. Den accidentally pushed some trucks into a ravine when the icy rails cause him to slip. The Fat Controller reprimanded him for this, but he took it all in stride realizing the occurrence was beyond his control.
They found the cold weather challenging, and He and Dart teased James about it even though they were colder than everyone else.
He was later seen working on a section of repairs of the Crater Lake Bridge.
Den is kind, intelligent, and always willing to work. He is a bit slow in saying his sentences and has to offer Dart's help, but he never complains about it and is good friends with Dart. His caution and patience are very well renowned among the engines.
- Season 1: Lift Bridge, Snow Blind (cameo), Shepherd's Pie (cameo), Scruff's Scaffolding (cameo), Wilbert the Lumberjack (cameo), Rendezvous with Disaster, Will Power, Conspiracy Theory
- Season 2: Scot-free (cameo), Mavis and the Tornado (cameo), James Goes on a Trip (cameo), Rock-Star, Munitions (cameo), Swan Dive, Aura of Menace (cameo), Swashbuckler
- Season 3: Samson, BoCo, and the Man in the Hills (cameo)
- Web Clips: Walter Sliggs - Meet the Characters! (does not speak), Percy's Kafka Dream (cameo)