Snape was friends with Lily
Rowling has stated that Snape is neither a hero nor a villain, which meant that every time he made an appearance, we never knew what was going to happen. Snape went off book many times, but one of the most shocking things we learn about his past is his relationship with Lily. Even though he spent six books bullying Harry, Snape cared deeply for Harry’s mother! Harry himself discovered this about Snape, which must have been one awkward experience.
The Marauders were Animagi
After a confrontation with his godfather, Sirius Black, in Harry Potter and the Prisoner of Azkaban, Harry learns that his father was an unregistered Animagus. Not only was James an Animagus, but his friends were as well! A group of teenagers illegally became part-time wild animals! As a reader, I was so focused on deciding whether or not to trust Sirius that I never saw the Animagi reveal coming!
Narcissa lied for Harry
As readers, we pretty much accepted that the Malfoys were an evil family. When Narcissa came on the scene, she seemed loyal to Lucius, Draco, and Voldemort as well. One of the most surprising moments of Harry Potter and the Deathly Hallows was when Narcissa lied to Voldemort. She essentially aided Harry’s cause! Yes, she didn’t change her allegiance and she only helped Harry for selfish reasons, but it was still unexpected. It takes a brave woman to betray the Dark Lord and Narcissa is certainly that!
Ginny opened the Chamber
In Harry Potter and the Chamber of Secrets, Rowling did an impressive job associating the hidden chamber with Slytherin House. Then we were thrown off the scent when Tom Riddle revealed that Ginny opened the Chamber of Secrets. I never imagined that Ginny was under Riddle’s control, even though Rowling did leave hints that something was wrong with her. Ginny was the last person you’d expect to be helping Voldemort, so it made for one amazing plot twist.