Sirius Black was an animagus, like his three friends at Hogwarts. As a big, black dog, he went by the name "Snuffles."

Cedric Diggory is the character who defies the stereotype of Hufflepuffs as bland nonentities. His sense of loyalty and fair play led him to accept Harry as his co-champion in the Tournament ... and ultimately led to his death in the maze.

Hagrid is the Hogwarts' groundskeeper. His love of dangerous magical creatures often gets him in trouble.

McGonagall observes the Dursley house very early in the series in her guise as a cat. She later shows off her transformation to the Gryffindors, before teaching them transfiguration.

Lupin was a fan favorite. Nonetheless, Rowling killed him in the final installment of the series.

Though Slytherin is sometimes thought of as the "evil" house at Hogwarts, it's actually the house for those who are ambitious, seeking power along with knowledge and skill.

In the last book, several beloved characters died in the battle of Hogwarts. One of them was Fred Weasley, whose twin, George, lost an ear.

"I am Lord Voldemort" was the anagram for "Tom Marvolo Riddle," the Hogwarts student who became the most feared wizard of his age. Marvolo Gaunt was his grandfather.

Neville had a famously bad memory and not a lot of courage in the early books. But he later became a charter member of Dumbledore's Army. The Internet activist group "Neville Fights Back" is named for him.

Cho was a Ravenclaw and seeker on their quidditch team. Harry worked up the courage to ask her to the Yule Ball, but she was already going with Cedric Diggory.

Barty Crouch Jr. imprisoned Alastor Moody in a trunk and impersonated him throughout "Goblet of Fire." The flask from which he nipped wasn't firewhiskey but polyjuice potion, which allowed him to keep up the ruse.

Lavender was Ron's girlfriend before he acknowledged his feelings for Hermione. Their relationship dismayed Hermione, who was more in touch with her feelings at that point than Ron was.

Snape treated Harry badly on the surface, but looked out for him when it counted. His patronus was a doe -- a symbol of gentle Lily Potter.

Harry's patronus is a stag because his father, James, an animagus, took a stag as his form. This is revealed in the third book, "Harry Potter and the Prisoner of Azkaban."

Draco and Harry met while shopping for school supplies before their first year. Draco was eager to make a high-status friend like "the boy who lived," but Harry was unimpressed with Draco's behavior and sense of entitlement.

When the third-year Gryffindors were learning to defeat boggarts, creatures that take the shape of a person's fears, Ron's took the shape of a giant spider. He defeated it by imagining it as legless and rolling around the classroom.

Sybil Trelawney successfully predicted that a boy would be born who would defeat Voldemort. However, the mystic gobbledegook of her class led Hermione Granger to drop out in frustration.

Dumbledore's sexuality is not made explicit in the books, in which he has no romantic attachments. But Rowling's announcement led a number of people to speculate about Dumbledore's relationship, in his youth, with the wizard, Gellert Grindelwald.

Bill Weasley was also a Head Boy in his time. But it was Percy whose badge Fred and George changed to read "Bighead Boy."

Vincent Crabbe and Gregory Goyle were Draco Malfoy's hangers-on/henchmen/bodyguards. They were almost interchangeable in the books, with no distinguishing characteristics from each other.

The quidditch teams in the Potter books were co-ed. Katie Bell served as Gryffindor's chaser for most of the years during which Harry played.

Ginny stole her brothers' brooms and practiced flying when they weren't around. She scored the coveted seeker position on Gryffindor's team this way.

Harry's rage at hearing his dead parents insulted by Marge Dursley led him to inflate her like a balloon, then run away from home. The Ministry of Magic had to deflate her and erase her memory of the incident.

Pansy is often at Draco's side, "simpering," as Rowling puts it. She also seems to have a special dislike for the Muggle-born Hermione.

Madam Pomfrey runs Hogwarts' infirmary. She considers chocolate to be an important magical remedy. If only that were true in the Muggle world.

Crabbe and Goyle were Slytherin's beaters. Draco Malfoy was the seeker -- a position that his father seems to have bought for him by purchasing high-performance brooms for the entire team.

Viktor Krum was a seeker on Bulgaria's national team. Later, as a Durmstrang student, he came to Hogwarts and fell for Hermione Granger.

Rowena Ravenclaw's daughter was named Helena. Not an entirely nice character, she stole her mother's diadem in an attempt to surpass her in intellect and knowledge. Why not just study hard, Helena?

Rita Skeeter is an unregistered animagus. She turns into an insect to spy on the subjects she writes about in the Daily Prophet.

Arthur Weasley loves all things Muggle, but doesn't always grasp the details. He calls a telephone a "fellytone" and electricity "eckletricity."

Hermione and Percy had several qualities in common. However, they never dated -- Percy had a Ravenclaw girlfriend called Penelope, and Hermione dated Viktor Krum, and then, of course, Ron.

Fleur and her sister are both part veela -- enchanting, siren-like creatures. Many boys were taken with Fleur, but it was Bill Weasley who won her.

Newt Scamander is the hero of "Fantastic Beasts and Where to Find Them." He was played by Eddie Redmayne.

Charlie Weasley goes to Romania to work with dragons. He returns to Hogwarts for the Triwizard Tournament, wrangling the dragons which will be used in one of the challenges.

Lucius owned Dobby. When Harry handed Lucius a dirty sock, the appalled Lucius tossed it aside, straight into Dobby's hands. The gift of clothing is a gesture which immediately gives a house elf its freedom, so Dobby was freed.