Oliver is a green Great Western Engine that Douglas saved from scrap.
Oliver and his brake van Toad were to be scrapped until Douglas came to their rescue. They escaped to Sodor and were properly re-painted and brought back into service. Oliver, after landing bunker-first into a turntable well and pulling a fiesty ballast wagon in two, found his niche on the Little Western Branch Line. The trucks occasionally play tricks on him, but he always finds a way to get his own back!
Oliver and Toad have been working dilligently on the Little Western Extension Project, and are often put on Ballast Detail. On one occasion, Oliver and Toad soared off the Lift Bridge due to a signal malfunction. Oliver was badly hurt when Henry smashed his trucks into his wreck, and the Fat Controller was very dismayed by the hysteria associated with his grand design.
When Duck had broken down, Oliver had to haul Duck and his freight cars all the way home so his passenger train could pass. When the rescue was over, Duck commented that being a "Really Useful Engine" was all about "Rising to the Occasion."
Oliver did not get a good vibe from Scruff at first when he arrived to help at the Little Western Extension Project (due to his name being similiar to S.C. Ruffey's!) but after seeing his work ethic, he was happy to have him as part of the team. Even after Scruff almost sent Mavis hurtling over the edge of the bridge, Oliver calmly came to the rescue and did his best to make Scruff feel better.
Although the Little Western is Duck's Branch Line, Oliver is becoming more and more independent. When Sidney came to the Branch Line to help with ballast work, Oliver was the one to take charge of the engines "emergency meeting" regarding Sidney's short-term memory loss. Oliver was always kind to Sidney, and exuded the sort of authority and respect that made Duck very proud!
He later noticed the Thin Controller picking up the Small Controller, and learned from Duck that it was a meeting from the Fat Controller. Oliver wondered if it had to do with the Little Western Extension, but Duck rebuked it.
During Richard Hatt's meeting concerning the new suggestion box, Oliver was the first to tease Duck about once again being used as a podium. Later, Richard read out Oliver's suggestion (to rename the Little Western to "Oliver's Branch Line"). Duck was not amused.
Oliver is a tough tank engine. He is often put-upon with adversity, but he has the strength and stamina to persevere. He loves working on the Little Western, and when Toad is not working with Douglas, the two make a grand pair. He is incredibly brave, but knows better now than to get too full of himself, which he admits, is a much more sagacious way of looking at things!
His experiences with nearly being scrapped and being on the run still haunt him to this day. The other engines are aware that Oliver suffers from terrible nightmares from time to time.
- Season 0: Old Groaner (cameo)
- Season 1: Lift Bridge, Stepney Makes an Entrance (does not speak), The Old Warrior (cameo), Redemption (cameo), Improvisation (cameo), Rising to the Occasion, Snow Blind, Scruff's Scaffolding, Wilbert the Lumberjack (cameo), Sidney, Conspiracy Theory (cameo)
- Season 2: Paxton and Norman (cameo), Scot-free (cameo), Mavis and the Tornado, Rosie (cameo), Pummeling Percy (cameo), Tag-Team (cameo), Munitions (cameo), Blunderbuss (cameo), Aura of Menace (cameo), Henry and Kurt (cameo), Swashbuckler, Self-Fulfilling Prophecy
- Season 3: Samson, BoCo, and the Man in the Hills (cameo), The Suggestion Box, Percy and Asbestos (cameo)
- Web Clips: Oliver's Seaside Dive (does not speak), Mike and Frank Banter: SLOTLT, ScarletFire, and EE93's Return (cameo), Philip and Daisy - Meet the Characters! (cameo)
- Oliver's 2006 rerelease model was used from Blunderbuss onwards in his cameo appearance with the rerelease 2006 Toad the Brakevan. In Oliver's Seaside Dive, his 2014 model was used.