Special shoutout to /r/FanTheories, whose slavish Potter devotion fueled much of this article.
It seems like happy coincidence that the most heroic children at Hogwarts were all sorted into Gryffindor. Just going by odds, it seems terribly unlikely. But what if that suspicion is correct, and Harry, Ron and Hermione were originally destined for different houses? After all, the alternatives seem to make a lot more sense.
Harry was born for Slytherin. Like the rest of the house, he's cunning, resourceful and ambitious. Draco Malfoy senses Harry's potential, and initially welcomes The Boy Who Lived with open arms. Plus, there's that part where Harry can talk to snakes. At this point, they should probably add a lightning scar to the snake on the house crest. We all know it's true: Harry could do great things in Slytherin.
Other than being the house with all the coolest, most kissable kids, Ravenclaw is known for valuing "intelligence, knowledge and wit." There is no one at Hogwarts who more embodies those qualities than Hermione Granger. She might be a little dweeby, but she outclasses everyone when it comes to academia, and has a tongue so venomous it could kill a Horcrux.
Ron Weasley and Hufflepuff were made for each other. We all know it's true.
As compelling as the theory may be, the fact remains that all three ended up in Gryffindor. Why? Well, because they asked. The Gryff values bravery above almost anything else, and if you're brave enough to request an invite, admission is guaranteed. That still doesn't explain Neville Longbottom, though.
Dementors have always had it in for Harry Potter. Granted, as hellish soul-eating demon creatures, they aren't really nice to anyone. But even before they sided with Voldemort in the wizarding war, the Dementors repeatedly dicked with the kid, starting with the time they suckled on Harry's soul on the Hogwarts Express.
Poor guy can't even play a Quidditch match without being assaulted by these dollar-store Ringwraiths.
Officially, it's explained that the Dementors are so attracted to Harry because of the extraordinary trauma in his past. But if that's true, why wouldn't Neville Longbottom be a target? His parents weren't killed, but they were tortured to the point of insanity, leaving them to spend their days in a magical mental hospital. That's
There's a much simpler explanation: The Dementors want a piece of Harry because they love souls, and Harry has more soul than anyone else. Remember, in addition to the soul that he was born with, Harry has part of Voldemort's soul inside of him. Combine a Horcrux and a human, and that's 1.125 souls -- or depending on who you ask, 1.015 souls.
No matter the math, Dementors are drawn to Harry because he's got more of what they love. For them, Harry's bonus soul is like getting two toys in your Happy Meal. They can't resist. If you've ever gotten seven chicken nuggets instead of six, you'll understand.