Frankie is a devious, shifty diesel engine who works at the Mainland Steelworks with Hurricane, Lexi, Theo, and Merlin. She is very controlling and manipulative, and can act rude to others. She also likes to speak her mind, but will often not know when it's too much. However, underneath that apathetic and crafty exterior, it is revealed that she only acted the way she did because she just wanted help from other engines due to the busy work schedule that she and Hurricane had.
Frankie is based on a Hudswell Clarke 0-6-0 diesel shunter which worked at the Manchester Ship Canal. (But the letters above her face stand for "Mainland Steelworks Company"