Millie is The Earl's private French narrow gauge engine. She works at Ulfstead Castle, she was introduced in season 14.
Appearances 
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- Season 13: How Gator Stole Christmas (mentioned; not named)
- Season 14: Millie's Castle Hassle, Freddie at the Ready and Cabless Companions (cameo)
- Season 15: Philip Finds a Friend (does not speak)
