Thomas the Tank Engine Wikia
Thomas the Tank Engine Wikia
This article is about the diesel engine. You may be looking for the Story Library Book.

Thomas has shown me that being a really useful engine is much better than being really lazy.”
―Dennis to Sir Topham Hatt[src]

Dennis is a lazy diesel who works on the North Western Railway. He has a twin named Norman.


Thomas & Friends

When Dennis was new to the railway, he tried to take advantage of Thomas by getting him to do all his work for him. He soon learned his lesson when he reversed into a ditch. With Thomas' help, he was able to finish his work and promised to be a Really Useful Engine from then on.

In The Great Discovery, Dennis and a number of other diesel engines were waiting in the quarry yard upon hearing that Thomas had been found in the days leading up to the reopening of Great Waterton.


Dennis is considered to be a very lazy diesel who tries to take advantage of others and depend on them to do his work instead. Dennis will often create excuses to get out of work and is infamous for the fact that, unlike most of the engines on Sodor, he does not make an effort on being really useful, and slacks off on a regular basis. As a result of his laziness, he is very unpopular with other engines, but they are forgiving enough to let him redeem himself, depending on how motivated he really is. He usually gets caught in his lies and always says sorry - but whether or not he means it is the question.

Technical Details


Dennis is based on British Rail (BR) 11001, a prototype Bulleid diesel built at Ashford Works, England in 1949 and scrapped in 1959. He also carries his basis' number. Dennis' twin, Norman, is also based on BR 11001.


Dennis is painted two-tone grey with dark grey wheels, gearboxes, roof, and front. His number 11001 is painted on his sides in white, and his jackshaft is red.


Voice Actors

Audio Files


First used Last used Sound Effect
Series 9 Series 9

On the Diesel's Locomotion Mayhem ride at Drayton Manor Theme Park, Dennis is incorrectly portrayed with Diesel's horn.

First used Last used Sound Effect
Drayton Manor Theme Park Drayton Manor Theme Park


  • According to a magazine article, Dennis lives at Vicarstown Dieselworks with Diesel 10, possibly an idea from the early stages of production for Day of the Diesels.
  • Dennis was originally intended to return in Day of the Diesels, however, he was later dropped and replaced by Norman, who is also based on the same engine as Dennis and is known as his twin.[3]
  • Dennis and Norman are the only twins to never appear onscreen together.
  • Dennis' horn sound comes from a stock sound effects pack and as such can be found in many other pieces of media. It was also mistakenly reused for 'Arry in the eleventh series episode Hide and Peep and Flynn in the twenty-third series episode Steam Team to the Rescue.
  • Dennis, along with Colin, Flora and Hank are the only characters introduced in the HiT Entertainment model era to not have a Capsule Plarail toy.
  • Dennis had a total of six facial expressions, one of which (a drowsy face) was never shown on-screen.
  • A character face checklist from the tenth series reveals that Dennis was originally going to be named Denzel.



* RWS only | ** T&F only | --- Dropped