Penny was an average girl with slightly spiky, dirty blonde hair in a ponytail. She was seen to be wearing what looked like a tattered and grubby school uniform. Sometimes, Penny floated in the air and flew around; she was able to do this because she was in fact a ghost.
Penny was the spirit of a young girl who died in a fire during a history exam one hundred years before the time of the episode. She came back once a year to haunt the history exam at Elizabeth's school. Neither the other pupils nor Miss de Burm, who was monitoring the exam, could see her ghost. When Elizabeth begged Penny to help her in her exam, Penny helped before disappearing. Unfortunately for Elizabeth, Penny was terrible at history too, and got every single question wrong.