Thomas and the Evil Diesel, retitled Thomas and the Naughty Diesel in American releases, is a book written by Christopher Awdry. It was later retitled Thomas and Diesel and included My First Thomas-style illustrations.
When Percy has to go to the Works for repairs, Diesel returns to Sodor and, as expected, causes trouble for the engines by destroying the oldest truck in Ffarquhar Yards. But two days later, Thomas has an accident when Daisy drips her oil on the track and Clarabel's back wheels come off the rails at the special points at Dryaw, so Diesel comes to the rescue. It seems that even Diesel has some good in him somewhere.
- Sir Topham Hatt
- Duck (absent in US release)
- Daisy (does not speak)
- Annie (does not speak)
- Bertie (does not speak, absent in US release)
- Gordon (cameo, absent in US release and My First Thomas release)
- The Random House version has less realistic illustrations and toned down dialogue.
- This marks Diesel's second appearance on Sodor.
- This book was written by request of the TV series producers, but was never adapted into an episode. However, Diesel being the only spare engine available was a plot device that Britt Allcroft would use in the TV series for the episode Diesel Does it Again. The World's Strongest Engine also uses this plot device.
- The Random House version, narrated by Robin Smith, was used as a bonus feature on the DVDs, Thomas Comes to Breakfast and Other Thomas Adventures and The Early Years (Disc 3).