I was rereading the Order of the Phoenix, and I stumbled upon something. When Harry asks Aunt Petunia how she know about dementors, she replied "I heard that awful boy telling her". Harry assumes she was referring to James. However, in Snape's memory in the Deathly Hallows, Lily says "Tell me about dementors again, Severus." That means JK Rowling had the whole series planned out for years. I hope I wasn't the only one who was mindf*cked.