Derek is a diesel engine with bad "teething" troubles. He works at Anopha Quarry.
BoCo soon came to Derek's rescue.
Unfortunately, Derek soon overheated when he came to a hill he didn't expect. He soon stopped; leaving Bill and Ben having to pull the train and Derek at the same time.
Derek is a friendly diesel engine with bad teething troubles. He overheats every time he comes to a hill; he is often found working at Anopha Quarry with Bill and Ben.
- Season 1: Toby and the New Engine
- Season 3: Cranky's Delivery and Donald Visits the Scrapyard (cameo)
- Season 4: Arthur Helps Out
- Season 6: The Haunted Shed (cameo)
- Season 7: Rails on Fire
- Season 8: Frank and the Fib (cameo)
- Season 9: Tender Bender (cameo) and Arthur and the Fights of the Brown Turntable
- Season 10: Lorry's New Flatbed and Coal Crisis (does not speak)
- Season 11: Stepney and the Bluebell Branchline (cameo), The Great Western Way (cameo), Just Duck's Luck (mentioned), Holly Jolly Molly (cameo) and BoCo and the Cocoa (cameo)
- Season 12: Greetings, Montague! (cameo), Stafford's Electric Slide (cameo) The Importance of Being Billy, Rheneas and the Risky Rendezvous (cameo), If The Dome Fits (cameo) and The Mystery Train (cameo)
- Season 13: Bert's Arlesdale Fail (cameo) and Ivo Hugh's Day at the Zoo (cameo)
- Season 14: Quarry Quest and Hiro and the Heat Wave (cameo)
- Season 15: Roundhouse Roulette (cameo), Harvey's Happy Accident and The Island of Misfit Engines (cameo)
- Season 16: Bad News Bear (does not speak), Bowler Strikes Again (cameo) and Paxman Pulls Through
- Season 17: Unidentified Flying Scotsman, Dustin the Really Useless Engine (cameo), Hard to Handel (cameo), Big Trouble on the Little Western (cameo), and Para-Norman Activity (cameo)
- Season 18: Santa Claws (cameo)
(not named; does not speak)