Marion is a self-propelled steam shovel. She works at the Sodor China Clay Company.
Marion works at the China Clay Workings. She is bubbly and friendly and loves digging, talking, and talking about digging. She is always ready to share her tales with the other locomotives, who sometimes try to avoid her. Thomas is always happy to hear her stories. Items she has claimed to dig up in the past include a pirate chest. She enjoys playing "Guess What's in My Shovel" with Bill and Ben although the answer is almost always mud.
The morning after a large landslide at the clay pits, Marion met Thomas for the first time, scaring him with her bucket. When she introduced herself, Thomas found that she talked a lot. A few days later, she was still cleaning up the fallen rocks when Percy and James came her way trying to escape from another landslide caused by James' whistle. Although James escaped, Percy was swept up by the landslide. He was buried wheel-deep when he saw a large rock coming his way. It looked like the end for the little green tank engine, but Marion put her bucket in front of him and caught the rock, which she identified as the skull of a Megalosaurus.
Whilst repairing an embankment on the main line, Marion once hit a water pipe, causing a leak. Marion decided to cover up the leaky pipe, but Thomas later spotted water trickling out of the ground. When he took Marion to inspect the site, water gushed up from the ground and caused a landslide. Luckily, Marion was able to clear the line just before Gordon raced through with the Express. Marion promised that she would tell someone if she unearthed a water pipe in the future.
Later, Marion became worried when Ben didn't bring any coal to the clay pits. She was cross when she realised that the twins had used it all up, and got them to thank and apologise to Timothy, who came to the rescue by fetching more coal for Marion and the twins.