Here's everything to know about HBO's 'Harry Potter' series, which may have recently cast its new Dumbledore After seven books, eight movies, one play and a whole spin-off series, Harry Potter is debuting on the small screen for the first time.

When asked about the offer to play Dumbledore, Lithgow described the decision as "not easy," recognizing it could define the final phase of his illustrious career.

Lithgow's casting breaks tradition of British actors in Harry Potter, sparking debate. HBO's American casting decision opens more opportunities for diverse talent in series. Auditions for lead trio ongoing, with Paapa Essiedu as Snape and Cillian Murphy as Voldemort rumored.