6. Dumbledore And McGonagall Were Lovers
The Theory: One of the oldest Potter theories lurking around online, the incredibly close bond shared by Professors Dumbledore and McGonagall has, by many fans, been thought to bear romantic connotations.
Threads from as far back as May 2007 - before the final book launched - would discuss the idea that the elderly teachers were in love, speculating that their friendship was actually a relationship.
Not much evidence was given to support these claims besides the fact that they've known each other for a really long time, are often seen together, and are on first-name terms (whereas a lot of other Hogwarts Professors use surnames). Despite this lack of evidence, Dumble-gall was a popular ship in the early 2000s.
The Debunking: Even after the book series concluded, Rowling continued to drop tasty nuggets of information for fans to gobble up. One of these came in October 2007, where the author revealed that Dumbledore was gay, stating that he had been in love with Gellert Grindelwald in his younger days.
Though not a direct dismissal of the idea that Dumbledore and McGonagall were in love, this revelation confirmed that their relationship had always been platonic, debunking the theory that they'd been lovers at some point during their Hogwarts careers.