Muggles' Guide to Harry Potter/Characters/Penelope Clearwater

Overview
Penelope Clearwater is a girl in Ravenclaw house. When she is first identified in Harry Potter and the Chamber of Secrets, we are told that she is in her fifth year, thus she is three years ahead of Harry. We also learn that she is a prefect. In later editions of the book, her year was changed to sixth year when we first meet her, for reasons described below.

Chamber of Secrets
Penelope Clearwater is first seen, although unidentified, at Christmas; Harry and Ron, disguised as Crabbe and Goyle, are wandering around looking for the Slytherin common room, and ask her for directions. Shortly after she rebuffs them, they run into Percy, who threatens them.

In April, Penelope Clearwater is petrified by the Monster in the Chamber of Secrets; Hermione is attacked at the same time. Percy is deeply shocked by this attack, possibly because he believed that Prefects would be protected by their office.

It is only at the end that it is revealed that Penelope is Percy's girlfriend; this explains the magnitude of the shock Percy feels when she is petrified, as well as explaining what she was doing in the school's lower levels at Christmas, near where Percy was. This also is the reason Penelope's age was changed in later book editions: first, until sixth year she could not be a prefect, and second, if she's in sixth year she's the same age as Percy, making it more likely that she could be his girlfriend.

Prisoner of Azkaban
Ron complains of having to use Errol for his correspondence because Percy has been sending messages back and forth to Penelope all summer, fully occupying Hermes' time.

While all the Weasleys are staying at the Leaky Cauldron preparatory to departing for Hogwarts, Percy accuses Ron (who is sharing a room with him) of spilling tea on Penelope's picture; apparently the image has some spots on her nose and is trying to hide behind the frame.

Before the Quidditch match with Ravenclaw, Harry brings his new Firebolt broom down to breakfast. Many other students come over to look at it, including Penelope, who asks if she can hold it. Percy warns her against sabotage, then later remarks that he has a ten-Galleon bet on the outcome of the game with Penelope. He later tells Harry that Gryffindor has to win, because he doesn't have ten Galleons.

Deathly Hallows
When Harry, Ron, and Hermione are trapped by Snatchers, Hermione claims to be Penelope Clearwater. Unfortunately, this ruse does not last, as her likeness in a newspaper clipping identifies her as one of the people believed traveling with Undesirable Number 1, Harry Potter.

Relationships with Other Characters
Penelope is Percy Weasley's girlfriend throughout the first three books, though it is unsure if their relationship still stands because she never directly appeared in any book after Harry Potter and the Prisoner of Azkaban. Percy's estrangement from the other Weasleys, up until the final book, likely left his family in doubt as to the state of his personal relationships.

There is no indication that Penelope and Hermione were friends while at Hogwarts, but in Harry Potter and the Deathly Hallows, Hermione, to hide her identity, claims her name is Penelope Clearwater when Snatchers capture her, along with Harry and Ron. Whether she chose this name because Penelope was still in a relationship with Percy at the time is unknown, though it seems more likely that the name randomly occurred to Hermione because it had a prior connection to the Weasley family.

In the Weasley family tree that the author created following the series, it is revealed that Percy marries one Audrey. We can, therefore, assume that his relationship with Penelope had ended some time earlier.