The fan theory: Draco Malfoy is a werewolf
At some point in the last ten years, people came together and decided Draco Malfoy was a werewolf.
Why? Well, the theory goes that Greyback bit Draco on Voldemort’s orders, as punishment for Lucius’s failure to retrieve the prophecy at the Ministry. Supporters of this theory believe Draco was never made a Death Eater, not officially; he, like Greyback, was promised a sort of informal allegiance in exchange for his services. There's a mountain of evidence for this, including 1) we never see Draco's Dark Mark, 2) Draco becomes very ill and pale over the course of the sixth book, and 3) Voldemort makes pointed remarks to Draco about babysitting Tonks and Lupin's werewolf cubs. If you want to know more, you can check out dracomalfoyisawerewolf.com, and I am completely serious about that.
I think we can all agree that the evidence is mostly conjecture. Besides, there’s no way Voldemort would ever dilute the blood of a loyal pureblood family. But that didn’t stop a bunch of us from saying, “YEP, THAT’S A WEREWOLF IF I EVER SAW ONE.”
The theory’s been debunked by J.K. Rowling herself, but here’s why I think it would’ve made for a better book. As someone who appreciates good storytelling, there’s something I like about the idea of Draco Malfoy ultimately becoming what he always hated most: a half-blood. Many of us were hoping to see a Draco Malfoy redemption arc at the end of the series, or at least something concrete to showcase his ideological shift. What we got instead were Draco’s fledgling attempts at almost doing the right thing, followed by some brief but significant eye contact with Harry in the epilogue. What better way to wrap up Draco Malfoy’s storyline than by forcing him to forfeit his status and privilege and learn compassion for a group of wizards he and his family had always considered inferior?