The very important reason why the Horcrux inside Harry didn't die when he was bitten by the basilisk.
What ~actually~ happened to Fluffy after he was finished guarding the Philosopher's Stone.
The reason why the pure-blood Black family's home was in the middle of a Muggle housing complex.
The reason why the Resurrection Stone still worked after the Horcrux inside it had been destroyed.
Fred's death was, for JKR, the most upsetting to write.
Moaning Myrtle's full name.
A little bit more about the reason Tonks's Patronus changed when she fell in love with Lupin.
Which Weasley twin was born first.
The reason why Harry didn't name either of his sons after the third marauder.
There is a wizarding school in the USA, but it's not in New York.
The reason why Wormtail – who ended up being Voldemort's most loyal servant – was sorted into Gryffindor.
There ~is~ a wizarding equivalent to the United Nations.
Tina and Queenie Goldstein from Fantastic Beasts are sisters, and are distant relations of Anthony Goldstein.
We never learned what Hagrid's Patronus would be, because he couldn't produce one.
2015 was the year James Sirius Potter started at Hogwarts...
...and, of course, he was sorted into Gryffindor.
Crookshanks would definitely win in a fight with Mrs Norris.
Sirius Black's birthday.
And, finally, the most important lesson of all: