Loony Luna

“The girl beside the window looked up.  She had straggly, waist-length, dirty-blond hair, very pale eyebrows, and protuberant eyes that gave her a permanently surprised look.  Harry knew at once why Neville had chosen to pass this compartment by.  The girl gave off an aura of distinct dottiness.  Perhaps it was the fact that she had stuck her wand behind her left ear for safekeeping, or that she had chosen to wear a necklace of butterbeer caps, or that she was reading a magazine upside down.”
This is how we are first introduced to someone who would become a major player in the plot of the remainder of the Harry Potter series, Luna Lovegood.  The fact that it took five books for us to meet such an amazing and entertaining character is one of the biggest flaws in the series, but is rectified by the page-turning demeanor of the aptly named “Loony Luna”.  Rowling introduces her to the reader as the personification of this nickname all of her quirks are in view from the start.  “She did not seem to blink as much as normal humans.  She stared and stared at Harry, who had taken the seat opposite her and now wished he had not,” she writes.  
All of these descriptions firmly implant the vision of a girl is not all-quite-there in the head, yet it does not take long before a curveball is thrown into her qualities; “Luna is in my year, but in Ravenclaw,” Ginny explained.  As all HP fans know at this point in the series, Ravenclaw House is reserved for only the most intelligent and wittiest of witches and wizards, and that someone as seemingly absent-minded as this Luna could belong to that house is a juxtaposition indeed.  
Order of the Phoenix is a turning point in the series, where the mood switches from the happier days of their youth into the transition of the final showdown.  Book 4 ended with a death, and the rise of Voldemort into his physical body; Harry is plagued by his dreams and the memories of his past and Rowling throws him an emotional bone in the form of Luna.  She takes a staple of the franchise that the readers are used to, the horseless carriages, to symbolize this change.  For the first time Harry sees that there is indeed a creature pulling the carriages, and as we come to find that is because he has witnessed death.  The newly-introduced Luna is there beside him though, “reassuring” him that he is “just as sane as (she is).”   What was once simply written off as another wonderful thing in this magical world, was in fact a hard and gruesome truth; a theme that would be repeated throughout the rest of Harry’s story.
Rowling manages to develop Luna into not only a light-hearted character that can diffuse situations with her aloof demeanor, but as someone with whom Harry can relate it to who has shared similar hardships.  She stands by Harry when others doubt him, and throughout the series never loses faith.  This odd girl was the perfect segue from the characters lighthearted approach to what laid before them during their earlier years at Hogwarts to the serious plot points that were about to ensue.