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

“It's a shame you're not an elephant, Sidney."
"An elephant? Oh, why's that, Whiff?"
"They say that elephants never forget!”
―Whiff and Sidney[src]

Sidney is a forgetful blue diesel who is good friends with Percy. He often takes goods trains to the Mainland.


Thomas & Friends

Sidney was one of the diesels who laughed at Percy's joke when the tank engine first arrived at Vicarstown Dieselworks. He appeared very briefly on a hoist without wheels. He was still on that hoist even after two years later and was often referred to as a Christmas decoration by the other diesels, literally being used as one by Diesel 10 as well. As a Christmas present, Percy gave Sidney a new set of wheels and he is now a really useful engine again.

In the eighteenth series, he (along with Diesel, Den and Dart) hid from Paxton. But after Paxton was unable to find them, Sidney, along with Den and Dart started to think that Diesel's joke went a little too far, but Paxton managed to find them again at the end of the day.

In the twentieth series, Sidney was sent by the Fat Controller to collect new wheels for Percy. Sidney was worried he would forget his job and let Percy down, so Thomas, Annie and Clarabel suggested that he sing a song to remind himself what to do. Sidney thought this was a great idea and started to sing his song until he stopped at Wellsworth to talk with Gordon. After talking with him, Sidney completely forgot the words to his song and while trying to remember what he was supposed to do, ended up running all around Sodor, first to Whiff's Waste Dump, then to the Sodor Animal Park. Eventually, he decided that it would be best to go back to Knapford to confess to Sir Topham Hatt that he had failed to complete his special job. But upon arriving, he found a crowd of passengers waiting impatiently for their train to Brendam Docks. Thinking that taking the passengers was his special, Sidney found some coaches and took them to the docks. The Fat Controller was waiting there by Percy's new wheels, grumbling about the forgetful diesel's lateness. When Sidney arrived, the passengers praised him and the Fat Controller reminded him that he still had to take Percy's wheels to the Steamworks. Sidney - who thought he had already completed his special - gladly accepted the supposed second special and took the wheels to the Steamworks, where Percy was waiting.

In the twenty-second series, Sidney shunted a flatbed with parts for a diesel engine but he did not know who they are for. So he became Special Agent Sidney and he and Paxton solved the case of the puzzling parts. The answer turned out to be Sidney himself who needed repairing.

In the twenty-third series, he was one of the diesels who got into trouble by not doing their jobs properly due to Diesel playing a trick on Rebecca so she could bring his steel to Ulfstead Castle. Diesel, however, got in trouble as Rebecca told him and the others everything that happened. Later, he got trapped in the Dieselworks along with the other Diesels.


Sidney is a very helpful, kind and easy going diesel engine, but he is also very forgetful. He starts his day at one location and ends up at another, not remembering how he got there. When it was his turn for repairs at the Dieselworks, he was hoisted up and had his undercarriage removed. Being patient, Sidney was happy to wait and wait and wait. He sat there happy to pass the time with any engine that happened to be visiting. Two years later, he still had no wheels, so Percy helped him during Christmas to get a new set of wheels and now he is back on track.

Technical Details


Sidney is based on a British Rail (BR) Class 08 diesel-electric shunter. In the real world, BR Class 08s were in fact the most successful shunting engines in the world with 996 of them built. Over seventy of them are preserved by heritage railways, such as the Dean Forest Railway and museums, such as the National Railway Museum. Around one-hundred BR Class 08s also remain in service on the national rail network.

Diesel, 'Arry, Bert, Splatter, Dodge, Paxton, Ulli, the Mainland Diesels and Fernando are also based on BR Class 08s along with the international orange, blue and Chinese diesels. Two BR Class 08s also appear in the Railway Series.


Sidney is painted navy blue with yellow lining and hazard stripes under his face. His coupling rods and front buffer beam are painted grey, but have faded into a rusty red colour. His paint is chipped in places and shows signs of weathering.


Official Description

From Official Website[1]

Sidney: Sidney is a bit of a forgetful engine. He starts his day at one location and ends up at another, not remembering how he got there! When it was his turn for repair at the Dieselworks, he was hoisted up and had his undercarriage removed. Being patient, Sidney was happy to wait...and wait...and wait. He sat there happy to pass the time with any engine that happened to be visiting.

Fun Fact: Sidney is based on a British Rail Class 08 Diesel-Electric Shunter.


Audio Files


First used Last used Sound Effect
Series 17 Series 23

In The Case of the Puzzling Parts, Sidney has a squeaky horn.


  • In The Ultimate Diesel Guide, it claims Sidney is always called by his nickname "Sid", he is only ever referred to by his full name rather than his nickname. He shares this dilemma with Norman and Paxton.
  • In some merchandising and books, Sidney's name is misspelt as "Sydney".
  • Sidney gained a headlamp in the same style as Diesel's in Big World! Big Adventures!, as well as a taillamp.
  • Sidney shares his name with Edward's fireman.
  • Sidney's horn sound is Paxton's, but three steps higher-pitched.
  • Sidney is the only diesel that was not named in the lyrics from the "Day of the Diesels" song.


“Sidney, how long have you been up there?"
"Erm, not very long Percy. I mean.. er.. I forget".
It's been about two years!"
"Two years?! That's a very long time".
"Yeah, I'm waiting for my wheels. I think the order's been misplaced.”
―Percy, Sidney and Norman discussing how long Sidney has been on the hoist waiting for new wheels, The Missing Christmas Decorations, seventeenth series
“Ha ha ha, he he he, a very special job for me.
All the way to Brendam Docks, to fetch a very special box!”
―Sidney singing his song, twentieth series


  • Take-n-Play (discontinued)
  • Wooden Railway (normal version, Holiday and Seaside versions; discontinued)
  • Minis
    • Classic Minis
    • Chillin' Minis
    • DC Super Friends Minis (as Mister Miracle and The Penguin)
    • Sweets Minis
    • Back to School Minis

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