Daisy is a Diesel rail-car, who has been known to consider herself "highly sprung, and right up to date!" She was brought to help run passenger services on Thomas' branch line, while Thomas was "indisposed" after running into the Stationmaster's house. She can be hard to please, most indignant, and highly opinionated. She is confident in herself and can sometimes boast of her abilities in particular situations, unconcerned, despite having never actually been in such a position before. She will sometimes presume she can show other engines a thing or two, despite knowing little on the matter, until she actually learns for herself. She now runs on the Harwick Branch Line with Ryan, managing the passenger trains while he handles the goods.
Daisy is based on the BR Class 101s built by Metro-Cammell. However she is a single railcar, whereas the real Class 101s were DMUs.