caution: spoilers for Harry Potter and the Prisoner of Azkaban follow
In
J.K. Rowling's
Harry Potter series,
Moony is the nickname of
Professor Remus Lupin, the
Defense Against the Dark Arts teacher in
book 3. This became his nickname because whenever there is a full moon,
Lupin transforms into a wolf, as he is a
werewolf. This is a result of a
werewolf bite he got when he was a small boy.
When he was a student at
Hogwarts,
Lupin was friends with
Harry's father
James, as well as
Sirius Black and
Peter Pettigrew. All four were unregistered
Animagi;
James,
Sirius, and
Peter became
Animagi so that they could help their friend
Moony out when he transformed. When he became a wolf, he was dangerous to others, so they would transform at the same time and keep him from causing any trouble.
To facilitate this,
Headmaster Albus Dumbledore had a tunnel built from
Hogwarts grounds to a run-down old house a little ways away from the rest of civilization, called
the Shrieking Shack. Whenever there was a full moon,
Lupin would travel through this tunnel to
the Shrieking Shack, along with his three friends, and stay there until he transformed back. To prevent other students from finding the tunnel,
Dumbledore had a tree installed over top of the opening, the
Whomping Willow, which would flail its heavy branches at any one who got too close to it.
When
Lupin was hired as a teacher by
Dumbledore, he regularly took the newly-discovered
Wolfsbane potion, concocted by
Professor Snape under
Dumbledore's instructions, to stave off his monthly transformations. When he forgets to take it in his rush to help
Harry,
Hermione,
Ron,
Snape, and
Sirius at the end of
book 3, he transforms; even though
Hermione had just exposed him as a
werewolf, no one had expected him to transform, and hysteria ensues, giving
Peter Pettigrew the opportunity to escape. After the entire encounter involving the seven of them comes to as much of a resolution as can be expected,
Lupin decides to resign when
Snape reveals his
werewolf status to the public, and this is the last we see of him. Watch for his highly anticipated return in
Harry Potter and the Order of the Phoenix in 2002.
for a more complete account of the incident alluded to here at the end of book 3, see Sirius Black. for more on Moony, see Professor Remus Lupin.