Penny is a charming yellow USRA tank engine with green on her, and is based on a SR USA Class 0-6-0T. Originally classified as the USATC S100 Class and designed for shunting duties in Europe during the Second World War, after the war fifteen of these engines were sold to the Southern Railway where they were used as dockyard shunters at Southampton. After falling to her death on the cliff where her love and mate Timothy had a similar fate as her's, she had a white-yellow and white-green livery with blue eyes and black lining.
Long ago on Sodor, Penny dreamed of being Timothy's for months, but when she heard that Timothy had died in an accident, she had to make her choice. In her case, it wasn't suicidal, because her brakes had failed while she was taking the mail, and she fell to the bottom of her cliff, taking her crew with her. She has her eyes closed before bracing for her fatal impact, and she's giving into her sorrow and saying whatever last words she could say. But for the long afterwards, unlike Timothy, and every year on the date of her accident, she runs again, whistling loudly, calling and crying for Timothy, her loved one.