1. The first Harry Potter novel was published in 1998, the same year the Battle of Hogwarts took place. Hence:
2. In Greek mythology, the seer Cassandra was cursed so that none would believe her prophecies. Professor Trelawney's great-grandmother's name was Cassandra.
3. The Mirror of Erised* shows a person's deepest wish. When Dumbledore looked he saw the same thing Harry did: his family happy and reunited.
4. Ron Weasley's Patronus is a Jack Russell terrier, which have been known to chase otters.
Incidentally, Hermione Granger's Patronus is an otter.
5. After Fred's death, George was never able to evoke a Patronus charm again.
6. After the Battle of Little Whinging, 13 people gathered at the Burrow to mourn Alastor Moody. Lupin was the first to rise to offer to look for the body.
Remus was later the first of those people to be killed in the Battle of Hogwarts, making Trelawney's prediction — when 13 dine together, the first to rise will be the first to die — come true.
7. J.K. Rowling has stated Voldermort's Boggart would take the form of his own corpse, since death was his greatest fear.
8. Sometime after the Battle of Hogwarts, Harry made sure Snape's portrait was hung in the headmaster's office. It originally did not because Snape abandoned his post.
9. Voldemort cannot love due to being conceived under the effects of a love potion.
10. Both Sirius Black and Fred Weasley, Hogwarts pranksters from two generations, died laughing.

