Gwen is smart, independent, kind and level-headed, stating her best quality is her inability to get excited over minuscule things. Her attitude at first seems very harsh and sarcastic, but she is not a bitter engine. Rather, she is cautious of whom she lets into her life. Beneath her tough exterior, there is a kind heart that has learned to trust as time has gone on. Despite her distaste for whatever "the sheep" are fond of, she actually does desire to be welcomed by the popular crowd, but she distances herself from it because she believes it is not where she belongs. She isn't afraid to stand her ground should her reputation take a hit.
Gwen is based on a New York Central Railroad J-3a Hudson built by Alco of Schenectady, New York. Ten J-3a Hudsons, 5445 through 5454 were built with streamlined shrouds designed by Henry Dreyfuss in 1938 in order to do heavy hauling at a greater speed, most famously hauling the 20th Century Limited between New York City and Chicago. Following a grade crossing accident with a sand truck in East Chicago in 1945, the J-3a's had their streamlining removed. All of the NYC Hudson locomotives were scrapped and only one Hudson tender converted into a generator survives. Connor is also a member of this class.
Gwen is painted black with teal lining.
- Gwen is based on the character of the same name from the Total Drama series.
- Gwen has been partially modified to work on British railways with a screwlink coupling and buffers on the back of her tender. She retains a streamlined cowcatcher on the front, so she is unable to shunt.