Oliver is a Great Western Railway 14xx auto tank engine who works on Duck's Branch Line. He has two Great Western autocoaches named Isabel and Dulcie, and a Great Western brake van named Toad, who he shares with Douglas.
Oliver escaped the dreaded scrapyards of the Mainland, mainly thanks to Douglas, but also as the result of sympathetic signalmen, luck, and using "goods only" routes under cover of darkness, with some close calls along the way. Despite his previous heroism and daring feats, Oliver is an engine who is willing to admit every day is a learning curve. When he was still new to Sodor, he let the other engines' responses to his courage, resource, and sagacity from his amazing recounts of daring escapes and adventures get to his smokebox and he became conceited. However, when troublesome trucks pushed him into the turntable well, he grew into a much more humble, settled engine and was far warier of trucks. But later, with some help from his brake van Toad, he did gain much respect and authority among the trucks when he showed his strength with the ringleader of the trucks, S.C. Ruffey, a little more than he had perhaps been intending. Oliver still has gumption, but is now a more obedient, sensible engine. He feels his responsibility on the railway deeply, is ever thankful for being aided in his escape from scrap by Douglas, and is a trustworthy, tenacious, plucky engine. However, he does occasionally have one or two temper problems and grumbles quite easily, but despite this setback, Oliver is still one of the more really useful, and well-behaved engines on Sodor.
Oliver is based on a GWR 14xx 0-4-2T. These engines were fitted with a mechanical system allowing the driver to control the locomotive remotely from the cab of an 'autocoach', such as Isabel. The particular engine Oliver is based on, No. 1436, was built at Swindon Works in the August of 1934 and worked until it was withdrawn in 1958. It was scrapped the following year.
In the Railway Series, Oliver is painted in the GWR's green livery with yellow lining, black wheels, a brass GWR numberplate on his cab side, and a brass safety valve bonnet. Before he came to Sodor, Oliver was painted in BR unlined brunswick green with late BR crest logo.
In the television series, his paint had faded by the time he was rescued, leaving him a rusty-red colour. After his rescue, he was repainted in unlined NWR green with a GWR crest and has remained so ever since.
In the Railway Series, he carries two builder's plates on the sides of his cab.
- Season 100 - Skiff and the Lighthouse, The Railcar and the Passengers, Oliver and the Coaches, The Crashing Kipper, Mike and James, Snowploughing at Christmas, Sidney Helps Out, and Skiff and the Dolphin
- Joe Mills (UK/US; eighteenth season onwards)
- Hikaru Midorikawa (Japan; third - seventh seasons)
- Yuta Odagaki (Japan; eighteenth season onwards)
- Piotr Bajtlik (Poland; eighteenth season onwards)
- Doriel Zohar (Israel; Sodor's Legend of the Lost Treasure)
- Mario Filio (Latin America; eighteenth season onwards; except Sodor's Legend of the Lost Treasure)
- Renato Hermeto (Brazil; eighteenth season onwards)
- Ion Abrudan (Romania)
- Denis Bespalyy (Russia; eighteenth season only)
- Anton Savenkov (Russia; nineteenth season onwards)
- Joe Mills gives Oliver a Cornish accent.
- Oliver is named after Oliver Wicks, who was a much respected member of Stroud Baptist Church. He was the Reverend W. Awdry's next door neighbour in Rodborough, Stroud.
- Recent information has revealed that there really was a 1436 on the Great Western Railway.
- Oliver's third season whistle sound was Gordon's at a higher pitch. The same whistle sound was later reused for Neville and Flying Scotsman.
- One of Oliver's models was on display at Nitrogen Studios but is now on display at the Hara Model Railway Museum in Japan.
- Oliver's theme from the Classic Series is a musical variation on the theme from the 1963 film The Great Escape.
- Oliver has had many modifications throughout the television series. These include:
- Season 4:
- His whistle sound changed to a lower pitched version of Duck's.
- Season 12:
- Thicker eyebrows.
- Tale of the Brave:
- Black side-rods and lamp irons.
- More hand rails.
- His boiler and cab windows are slightly smaller.
- His whistle guard became slightly taller.
- The 'GWR' logo, his number, and his trailing wheels are slightly bigger.
- His driving wheels are slightly further away from each other.
- His bufferbeam is significantly smaller.
- His running board was painted black, like it was in the Railway Series, and is also thicker than on his basis.
- The frame around his coupling hook changed to black.
- He lost his guard irons on his cab windows, the counterweights on his wheels, his middle lamp iron and the lamp iron on top of his smokebox.
- His smokebox saddle is narrower.
- His top feed has moved forward slightly.
- He is slightly taller, but is also noticeably scaled down compared to his model form and his basis.
- His dome is taller and thinner.
- His funnel is thinner and less detailed compared to his model form and his basis.
- He gained rivets on his smokebox and on the sides of his bufferbeams.
- He gained a permanent headlamp and taillamp.
- His whistle design changes
- Season 19:
- His siderods became grey again.
- The rivets on the sides of his bufferbeams have changed to red.
- The frame around his coupling hook became red again.
- Season 100:
- He slightly increased in size.
- Season 4: