Timothy loves to work at the China Clay Pits with Bill and Ben, but his naïvety can sometimes lead to the twins playing tricks on him. Despite this, Timothy just dismisses them as silly and gets on with his job.
Bill and Ben tricked Thomas into taking a train of trucks, unaware that Timothy was on the other end which Timothy claimed was a bit of a funny trick. He gave Thomas some advice about the dangerous crumbling clay pit walls and he also told him not to mind Bill and Ben's tricks so much. Thomas accepted Timothy's advice to be careful.
Bill and Ben once teased Timothy for being an oil-burning engine instead of a regular coal-burning engine. Timothy started to get upset by this, but ended up having the last laugh when the clay pits ran out of coal. Timothy collected some coal from Brendam Docks and the twins finally apologised for their teasing. Sometime later, the twins sent him on a wild goose chase to Brendam Docks to find them a multi-coloured truck which they claimed that they wanted for doing something important which was one of their usual tricks, causing Timothy to run around the island until he came across a waste truck covered in red, orange, yellow, green, blue, indigo and violet paint. Salty claimed it to be a "rainbow truck". Timothy took the truck back to the China Clay Pits where Bill and Ben could smell the rubbish inside the truck. The Fat Controller scolded Bill and Ben for their silly trick they played on Timothy and were told to take the truck to Whiff's Waste Dump as a punishment, so the China Clay Twins took the multi-coloured truck to the Waste Dump and got into an argument on the way which caused the China Clay Twins to call each other a stinky tank engine because the truck was smelly.
One time, Bill and Ben constantly said Timothy was "no help at all" whenever they made mistakes, though no one was fooled. However, they convinced the Fat Controller to send Timothy to Brendam Docks to help Porter, who was working on his own due to Salty working on the mainland. But without Timothy, the work at the clay pits piled up. Finally Timothy came back with Salty and Porter behind him to help clear up the mess.
Timothy is friendly, helpful, and loves being really useful, but can also be naïve and gullible, which can lead him to fall victim to Bill and Ben's tricks. He is also strong-willed and determined.
Timothy is based on an open cab oil burning steam locomotive built by Bell Locomotive Works, Inc. of New York City. These engines, which were built in a variety of gauges, were used throughout the United States, Cuba, Central America, and South America in construction and industrial work, such as clay pits.
Timothy is painted dark blue with red lining and brass fittings. He has "SCC" written on the sides of his water tank in yellow and has gold nameplates with his name written in black on the sides of his oil tank.