Diesel eventually became a permanent resident of the railway, and continued to feud with the steam engines. However, his personality has begun to soften. He was silently thankful when Thomas replaced his water-contaminated oil and agreed to help the steam engines to complete an important job for the Fat Controller.
Diesel is based on a British Rail Class 08 shunter.
Appearances in Christmas specials
- "Thomas and the Missing Christmas Tree"
- "The Missing Christmas Decorations"
- "Last Train For Christmas"
- "Diesel's Ghostly Christmas"
- "Kangaroo Christmas" (stock footage cameo)