The idea was inspired by the Wizard’s Chess scene in Harry Potter and the Philosopher’s Stone in which Ron plays as both a knight and the king - the symbolic roles that Ron and Dumbledore play, respectively, in the greater wizarding war.
The wand chooses the wizard, we all know that. But Neville chose to adopt his father’s wand instead of getting his own. Only after Dolohov destroyed it and Neville had to get a new wand at Ollivander’s did he become better at casting spells.
Based on The Tales of Beedle the Bard, Harry is the invisibility cloak brother, Snape is the resurrection stone guy, and Voldemort is the Elder Wand sibling. Dumbledore, prior to Harry, possesses all of the Hallows - just like Death in the tale.
Rita was banished from living in the magical world for fabricating her stories. We assume she then went to live with the Muggles and fell upon difficult times, so she turned to writing about the wizarding world in an effort to make a living for herself.
Voldemort was BFFs with Fenrir Greyback, a werewolf known for infecting teenagers so that they grow up to resent humanity. He enlisted Greyback to bite the children of Death Eaters who have failed him - just like Lucius Malfoy did!
All the Weasley names except for Ron are either the names of a British king or queen or an Arthurian name. King George III was deaf in one ear and he became king because of the untimely death of Prince Fredrick.
The killing curse was originally used to cure disease (or “kill”) bacteria and viruses. This makes even more sense because at one point, people thought that “abracadabra” could cure the symptoms of the bubonic plague.
Apparently, after Fred’s death, George uses the Time Turner to travel to another place and time to become someone new and fulfil the dream of creating a mischievous paradise for kids and adults as an homage to his brother. Makes sense!