Hermione Granger played by Jim.
Hermione is a young witch.
Jim is a rather gung-ho roleplayer, interested in action, cool fight scenes, and lucrative spoils over careful consideration or puzzle solving. He frequently acts before he thinks, which includes fixating on his own strange explanations for setting details that the GM hasn't explained yet.
Ron Weasley played by Ben.
Ron is a young wizard.
Ben is a thoughtful roleplayer who tries to think through the best course of action within his character concept and the setting. He enjoys coming up with clever ways to justify the success of his plans within the premises of the setting.
Harry Potter played by Sally.
Harry is a young wizard.
Sally is Ben's younger sister. Ben took her along to the game on the first evening when his parents couldn't get a babysitter for the night. The GM quickly generated a young wizard character for her to play so she wouldn't get bored. She enjoys the make-believe aspect of the game, but has some trouble separating it from reality.
Professor Dumbledore is the headmaster of Hogwarts School of Witchcraft and Wizardry. He administers from his office in a tower. His main concern is recovering the mystical Lost Orb of Phanastacoria, a powerful sorcerous artefact capable of protecting his students from any attack.
Professor McGonagall is the head of Gryffindor House at Hogwarts. She is 70 years old, and was elected head of Gryffindor due to her great wisdom and popularity. How exactly she retains these at her age is a mystery.
Rubeus Hagrid is the Gamekeeper of Hogwarts. Dumbledore trusts him implicitly, but Hermione suspects Hagrid is up to some sort of nefarious plotting behind the headmaster to take absolute power into his own greedy hands. Who is right remains to be seen.
Professor Snape is Potions Master and leader of Slytherin House at Hogwarts. As such, part of his job is to keep the headmaster out of trouble, which seems to be a very difficult thing to do with young wizards and witches around.