Den is a Big Hydraulic Diesel Engine.
- Season 12: The Mavis Matrix (does not speak), Rheneas and the Risky Rendezvous (cameo), Bulgy Takes the High Road and Sidney the Renegade (does not speak)
- Season 13: Sam I Am and How Gator Stole Christmas (cameo)
- Season 14: Millie's Castle Hassle (does not speak), Merlin the Magical Engine, Dirty ‘Arry,
- Season 15: Ice Ice Daisy
- Season 16: Bye Bye Bertie (cameo), Bad News Bear, Bowler Strikes Again (does not speak), Paxman Pulls Through
- Season 17: Diesel Gets the Bronze
- Season 18: Santa Claws