There are some die-hard "Harry Potter" movie fans that have pored over the films, watched the DVDs repeatedly, not to mention obsessed over its bonus features too. There are actually some interesting behind-the-scenes secrets revealed in these features, which fans might be thrilled to read about.

Movie Pilot has diligently compiled these details. In "The Sorcerer's Stone," fans found out that lead actor Daniel Radcliffe had gone through 160 pairs of glasses while filming the whole movie series (looks like the healing spell Episkey just didn't do the trick).

Tom Felton, on the other hand, was unfamiliar with the "Harry Potter" books prior to being cast as Draco Malfoy. When the director asked which part of the book was his favorite, he answered Gringotts because he overhead the actor before him answer that. The director saw through him though, but luckily for Felton, thought that he was hilarious.

While filming "The Chamber of Secrets," Emma Watson would regularly bring her pet hamster Millie to the set. But when she died shortly after shooting started, the whole set department condoled with the actress by creating a coffin lined with velvet for Millie.

The director for the third film "The Prisoner of Azkaban" Alfonso Cuaron has a very thick Spanish accent, so when he described the demontors' effect to turn rain into "ice" on the Hogwarts Express, the visual effects team actually heard him say "eyes" so they drew eyes falling from the sky on their storyboards before Cuaron corrected them.

Watson looked extremely gorgeous when Hermione made her entrance to the Yule Ball, but the actress actually fell down and tripped on her dress while they were filming that scene for "The Goblet of Fire." And for his role as Professor Severus Snape, Alan Rickman actually had to wear black contact lenses.

Fans learned in "Order of the Phoenix" that Rickman also forbade Rupert Grint (Ron Weasley) and Matthew Lewis (Neville Longbottom) from going near his new BMW since they spilled milkshakes in his old car while filming the fourth film.

For "Half-Blood Prince," Dame Maggie Smith, who plays Professor Minerva McGonagall proved that she was one dedicated actress since she went through radio therapy treatment for breast cancer while filming the fifth film. Incidentally, it was the only film from the series that was nominated for an Oscar for Best Cinematography.

For part one of "Deathly Hallows," the prop department made 40 versions of Slytherin's locket since Radcliffe and Grint had to destroy them for one scene. And for part two, it was learned that Radcliffe used his wand as a drumstick so he broke 80 of them while filming.