Rosie

Rosie is a lively American little tank engine who idolises and loves Thomas, which sometimes bothers him. She works as both a shunting engine and a mixed traffic engine.

Personality
Rosie is a friendly, crazy, creepy, absent minded goofball tank engine who likes Thomas very much. She likes him so much that she will sometimes follow Thomas wherever he goes like she's his pet or something. She also considers her and Thomas to be in some sort of relationship (despite Thomas not being interested in her), and this can sometimes cause her to attack or berate any female engine that is around Thomas for more than 2 minutes.

Rosie can be described as a feisty, energetic and absent minded tomboy who is not afraid to do hard work.

Trivia

 * A reason why Thomas doesn't like Rosie is because he's asexual. Meaning that he's incapable of liking either gender.
 * Rosie is often naive to the insults and torment that Thomas gives to her because she's so blinded by her love to him.