- "Orange black. He looks like a tiger or something."
"Or at least trying to be one. It looks like we have a copy-cat on our buffers."
- ―Bill and Ben, Marion Saves the Day
Billy first arrived on Sodor when help was needed at the Shunting Yard. The Fat Controller told Thomas to show him around, but Billy was too cheeky to listen to Thomas! He eventually learned his lesson, but he can still be a bit unruly.
Nowadays, Billy likes to help out on the branch lines whenever he can. His favorite line of work is helping out on the farms.
He was later assigned to work at the China Clay Works after Bill and Ben lured Derek onto a landslide. His refusal to listen to Bill and Ben at first enabled him to avoid their tricks, but when he first encountered Marion, he grew extremely annoyed by her constant chatter, which was all well and good, though his put-down of her was far too malicious of a response to quiet her. His refusals to listen to Bill and Ben, who were determined to pay him out for his rudeness, resulted in him getting diverted to a siding, where his whistle caused a landside that Marion had to clear away. Billy, grateful, apologized to Marion, and the two started off fresh.
Billy is a bubbly, boisterous and silly tank engine that doesn't listen to anyone but authority. As a result, he is quite unruly and unsophisticated, and states that he values his independence. He is also rather short-tempered and impatient, and can be incredibly malicious if sufficiently annoyed. Despite this, he is still capable of being humbled, and is a good engine at heart.
- Season 2: Munitions (cameo), Blunderbuss (cameo), Henry and Kurt (cameo), All the World's a Stage (cameo)
- Season 3: Marion Saves the Day, Logan Leaves his Mark (cameo), Derek and the Two Faced Engines (cameo), The Suggestion Box (cameo), Ice Breaker (cameo), Percy and Asbestos (cameo)