The list of theories and hidden elements from the Harry Potter books that the upcoming reboot TV show can touch upon is growing every day. Though there's a lot of pressure on HBO's series, there are also many opportunities for growth and development. The length and scope of the show can be used to incorporate parts of the story that the movies omitted. While it's understandable that the films couldn't include every single aspect of the books, there are details within the books that add to the lore and foreshadowing of the world that must be touched upon.