One former Harry Potter actor shares advice for the person who will take over their role in the TV series. The Harry Potter movies began in 2001, starting with the release of Harry Potter and the Sorcerer's Stone. The series came to become a multi-billion dollar entity, becoming one of the most successful film series of all time. In the years following the movies' completion, HBO announced the development of a Harry Potter TV series. The show will feature an entirely new cast, allowing for fresh portrayals of its characters.