HBO's 'Harry Potter' reboot has cast key characters from the four Hogwarts houses. The cast includes the main trio, as well as professors and other notable characters such as Snape and Draco. However, it is unclear if the series has already started filming or if casting is still ongoing, with some reports indicating that filming has begun and others stating that the casting team is still looking for actors to play certain roles, such as Colin Creevey.