Nobody knew exactly why the Seventh Year Ravenclaw had done it. Some speculated that he'd been trying to kill Harry Potter. Others speculated that he had figured that casting the spell on Harry Potter during the Sorting would be the most public way to prove whatever theory he'd been working on or show off whatever experimental spell he'd created, since an unmodified version of the Gemino Curse wouldn't work on a human being.
It had been in the middle of the Sorting, and Harry's name had just been called when it happened. As the boy separated himself from his peers in the waiting line of First Years to make his way to the hat, the Seventh Year Ravenclaw had leapt up and cast what most people believed was the Gemino Curse due to the effect, seeing as nobody could clearly remember the incantation the boy had used before he had been killed in the ensuing scuffle that had been meant to subdue him so he could be questioned.
What happened next had caused an uproar. Where there had been one Harry Potter, there was now four. In the confusion that surrounded the incident, everyone had lost track of who the original was, and couldn't vanish the extras for fear that one of the "extras" was in fact the original. To make matters worse, it would soon be revealed that all four Harrys shared the same memories and each believed themselves to be the original.
After three long days and nights in the infirmary where he'd been poked and prodded by a wide range of experts in a number of fields who had been hastily called to Hogwarts, Harry Potter was finally sorted. All four of him. The sorting nearly hadn't happened as a number of experts had wanted to take the quartet to St. Mingo's for experimentation, but a sudden wave of public pressure that had seemingly come out of nowhere had been placed on the Minister who had found himself forced to call back the experts and allow the Harrys to continue their schooling like normal students who were suffering from an illness that didn't confine them to the infirmary.
As each Harry who had plenty of courage, didn't have a bad mind, and would have done well in Slytherin sat down at their house tables, they found themselves wondering how long they would be staying. With the Gemino Curse, the duplicate objects eventually vanished. The experts who had been consulted believed that three of them would do the same, and nobody knew exactly when that would be, or what would happen when they did.
For the time being though, Harry seated himself next to Ron who looked somewhat concerned for him. He'd been the first to be sorted, and had begged the hat not to put him in Slytherin. As he watched another one of the other Harrys be sorted into Slytherin, he wondered why. They were the same person, weren't they? Wouldn't he have also begged the hat to not put him in Slytherin?
As Harry sat down next to Ron, Harry seated himself at the Slytherin table, doing his best to avoid Malfoy and his book-ends who were speculatively scrutinizing him much like everyone else in the house. They were probably wondering how a pair of people who were supposedly completely identical to each-other could end up both in Slytherin and Gryffindor. He knew how, but wasn't about to share with the rest of the class.
While Harry and Harry were seating themselves, Harry made his way to the Ravenclaw table. He had asked to be put somewhere other than Slytherin and Gryffindor for several reasons, not the least of which was the fact that he didn't want to be there to witness it if his counterpart vanished rather than him. It was possible that it could be both extremely painful, and extremely gruesome, and he had no desire to watch himself die. Especially considering the fact that it would mean that there was a two in three chance that he too would soon follow. The hat told him that it had told the other two that they didn't have a bad mind, so Ravenclaw wasn't too far-fetched a choice for him.
As Harry and Harry sat down and Harry made his way to the Ravenclaw table, Harry sat down at the Hufflepuff table. He vaguely remembered something about Helga Hufflepuff saying that she'd take the rest in the song the hat had sang three nights before, and he was the rest. The girl who he sat down next to smiled and introduced herself and the girl who was seated to her right. They both seemed friendly enough. Maybe he could grow to like it here.