Marion is a self-propelled steam shovel who usually works at the clay pits with Bill, Ben and Timothy. Marion is very enthusiastic and likes to think of herself as well-informed and is happy to share her knowledge. She is very talkative and loves to tell stories of her discoveries. However, not all the engines prefer to stick around and hear her stories. Despite her enthusiastic demeanor, she can also be rather stern, as seen when she told off Ben for not delivering any coal and making the twins apologize and thank Timothy.
- It is currently unknown when Marion will appear.
- Marion does not have any front windows, making it difficult for her crew members to see.
- Marion has a rear coupling hook, but her coal bunker is in the way to couple anything up to her. This implies that her bunker may be retractable.
- Marion's name is derived from her basis (the Marion Revolving Steam Shovel) as well as the company that built her (the Marion Steam Shovel Company).
- Marion apparently has a rock collection.
- Marion is the first female character who Toad has referred to as Miss.
- Marion rediscovered Glynn behind some trees while working on Thomas' Branch Line.