Prompt: Hogwarts' new Muggle Studies Professor

Following the War, Hogwarts is in dire need of a new Muggle Studies Professor, one that has ample knowledge of both worlds, great skill as a teacher, and no fear of treading on toes or angering powerful people. After a long night of reviewing students, McGonagall comes across the old records of an utterly brilliant but eccentric student who disappeared long ago.

Via Arthur Weasley, she sends a letter to this prospective teacher, a frizzled-hair woman with a chameleon familiar.

Within days, she sees a school bus parked on the Hogwarts grounds.