Harry Potter and the Prisoner of Azkaban
House: Ravenclaw, 7th Year; Prefect
Percy Weasley's girlfriend, who is in Ravenclaw. The two have a bet on the Gryffindor vs. Ravenclaw Quidditch match. Luckily, the Gryffindors win, since Percy didn't actually have the money he bet Penelope. We assume that Penelope doesn't mind listening to Percy carry on about his Head Boy status.