Pottermore is a gold mine of interesting canon facts. Some of these are brand new but other facts just relate events and characters we’ve encountered before. Some other facts are clearly included to answer fan questions or explain perceived mistakes in canon. Here are a few particularly fun tidbits of canon information that make connections to elsewhere in canon:
Gamp was the first Minister for Magic, taking the post in 1707, a few years after the imposition of the International Statute of Secrecy in 1698. Cool connection: Gamp’s portrait is the one found in the corner of the Prime Minister’s office. Gamp is described in HBP1 as a “froglike little man wearing a long silver wig who was depicted in a small, dirty oil painting in the far corner of the room.” Name connections: Sirius Black (1877-1952) was married to Hesper Gamp (BFT). Presumably also connected to the creator of Gamp’s Law of Elemental Transfiguration of which there are five exceptions, one of those being that food cannot be produced out of thin air. (DH15, DH29).
And while we’re on the subject of Ministers for Magic, note that only five of those folks were from the twenty-eight “truly pure-blood families” listed in the ‘Pure-Blood Directory’ published anonymously in Britain in the 1930s. They are Hector Fawley, Radolphus Lestrange, Perseus Parkinson, Damocles Rowle, and Kingsley Shacklebolt.
Warbeck appears in the books, of course, but she is also mentioned in a variety of other places in canon. Two notable events in the famous singer’s career mentioned on Pottermore — the collision of three broom-riding fans over Liverpool and her opposition to restrictions on the ways witches and wizards would be allowed to celebrate Hallowe’en –were first mentioned in the Daily Prophet newsletters in 1999. Adverts for Warbeck’s concerts appeared on Rowling’s original website, including the price of five galleons for tickets (about 25 pounds). In QA7, Warbeck is mentioned as having recorded the Puddlemere United team anthem, “Beat Back Those Bludgers, Boys, and Chuck That Quaffle Here,” and sold copies as a fundraiser for the hospital, a fact also noted on Pottermore.
Ever since these skeletal horses first appeared in canon, fans have questioned why Harry didn’t see them after Cedric’s death, when the students were taking the carriages back to Hogsmeade Station. Rowling answered this question in the FAQ section of her original website:
I’ve been asked this a lot. Harry didn’t see his parents die. He was in his cot at the time (he was just over a year old) and, as I say in ‘Philosopher’s Stone’, all he saw was a flash of green light. He didn’t see Quirrell’s death, either. Harry had passed out before Quirrell died and was only told about it by Dumbledore in the last chapter. He did, however, witness the murder of Cedric, and it is this that makes him able to see the Thestrals at last. Why couldn’t he see the Thestrals on his trip back to the train station? Well, I didn’t want to start a new mystery, which would not be resolved for a long time, at the very end of the fourth book. I decided, therefore, that until Harry is over the first shock, and really feels what death means (i.e., when he fully appreciates that Cedric is gone forever and that he can never come back, which takes time, whatever age you are) he would not be able to see the Thestrals. After two months away from school during which he has dwelled endlessly on his memories of the murder and had nightmares about it, the Thestrals have taken shape and form and he can see them quite clearly.
She also answered this question in interviews. Now that her original website is no longer available online, she uses Pottermore to post essentially the same response.
Trelawney‘s first name
The spelling of Trelawney’s first name is different in the British version than it is in the U.S. version. The British version has “Sybill” while the U.S. version has “Sibyll.” On Pottermore, Rowling writes
My American editor wanted me to use ‘Sibyl’, but I preferred my version, because while it keeps the reference to the august clairvoyants of old, it is really no more than a variant the unfashionable female name ‘Sybil’. Professor Trelawney, I felt, did not really qualify as a ‘Sibyl’.
This partially explains the spelling difference, but not completely.
It does, however, bring up an interesting facet of Rowling’s personality. She should be able to say what the correct spelling is, and that should be the final word. However, she doesn’t tend to do this, instead allowing others to change things in “their” version of her work. This quirk also comes through in her not insisting that the filmmakers use her pronunciation of Voldemort’s name (she doesn’t pronounce the final t). It also makes it even more clear that we can’t assume that anything in the films is canon, since she just doesn’t insist on things like that. Only on Pottermore do we know that her own vision for Harry’s world comes purely through.