Harry sat at the table in the great hall, staring down at breakfast nervously as students chatted loudly around him. It had taken another week of testing the resulting potion and charms to make absolutely sure he had everything correct but finally, finally he was done. And everything was ready.
He had taken a seat on the other side of the table that he normally used so that he was able to see everyone throughout the hall. He wanted to be able to see it happen. He had worked so hard on this, and for so long. It was a miracle that nobody had caught what he was doing to be honest. According to Ron he had apparently started muttering in his sleep about it, but the freckled redhead just threw a pillow at him and told him to shut up, half asleep himself. He slept with a silencing charm around his bed after he learned that.
His eyes slipped along the table and the hall itself, taking in everyone's faces. It was the last he was going to see them for a month or two, after all. Well, sort of. He didn't know exactly how long the dose he had the house elves put in everyone's meals would last, but it should be around that time.
Glancing back down at his food, he smiled internally to himself. He shouldn't leave himself out. This was a gift to him just as much as it was a prank on everyone else. He took a bite of sausage, realizing he couldn't taste the potion in the food. Luckily Dobby, that fantastic elf, had confirmed for him that it was in everyone's food. The house elves had been more than happy to help the Great Harry Potter Sir pull off his prank.
He continued to nibble on his food for a while, nerves wracking him as he waited for everyone to show up and eat. Once the tables had been filled out, he nodded to himself. It was now or never.
"Harry?" Hermione's voice interrupted him as he slowly drew his wand under the table.
Startled he glanced at her and smiled widely. "Yeah Hermione? What is it?"
Instantly her face became guarded and stern, seeing him smile like that. "You're nervous. You're only that nervous when you're about to do something that I don't like. Whatever you're about to do, don't do it."
He smiled sadly at her and finished drawing his wand, pointing it upwards and slightly forward under the table. "Sorry, 'Mione. This is for everyone's own good. I'll see you in a month or two. Araectus Hidus."
With a clockwise twist to his wand and the spell leaving his lips, he forced his magic into the table and throughout the hall, filling it completely with the spell. The more magically sensitive of the students and staff suddenly felt a small sensation wash across their body, and felt something change. It was done.
Harry looked at the somewhat familiar person sitting across from him, and smiled. It had worked. She looked at him, confused. There was puzzlement in her eyes as she stared at him for a few moments then shook her head, her bushy hair flinging around herself.
"I'm sorry," she said, still sounding incredibly confused. "Who are you?"
He smiled widely at her. "Nice to meet you. I'm Harry Potter. What's your name?"
"Hermione Granger." She said, still confused. "I'm sorry it's just, I have the oddest feeling. Have I met you before?"
The potion and the charm worked together as a sort of mind magic. The potion forged a connection between the magic of everyone who ingested doses of the same batch, linking up any one spell that was cast on one of them next. It was quite dangerous in the wrong hands, but thankfully the potion was incredibly tricky to make, and the results barely lasted for two hours before it would wear off. With the modifications the Twins and Harry made to the potion however, it also magnified the next spell cast. A color changing charm that was only supposed to work for a minute and affect only a nail would instead affect the whole body and would last a day!
The charm however, that was the real magic. He had been lucky to find it at all! It had been in the restricted section of course, but he had broken into there in his first year so that wasn't much of a challenge.
The charm forced a shift of sorts in how the brain processes the links between a face, a name, and the memories of a person. The end result being when you looked at someone you knew while under the effects of the charm, you didn't know who they were. After they gave you their name again you'd be able to recognize them by that name, but your mind still wouldn't give you any preconceived notions about them.
Typically the charm could only affect one specific person you knew, but that's what the potion was for. Technically speaking, it still only affected one specific person. Just a different person for each of them who was connected. And since they were all connected, they all shared the magic making them unable to link the person to the name.
The end result being that every student knew who they were, and they knew the names of every person who introduced themselves, but they didn't know anything else about the person. Or rather, they couldn't remember ever meeting them.
Luna hummed happily to herself, continuing to eat breakfast as everyone else at the tables talked amongst themselves, confused and introducing themselves for the first time. She knew what had happened, of course. Harry Potter had given her a chance, not that she'd be able to thank him for a while.
She glanced up as a the boy sitting across from her turned to face her. "Hello, I'm Terry Brook. Do you have any idea what happened?"
She smiled at him happily and held out her hand to him. She didn't know who he was. "Luna Lovegood. And no, I'm just as in the dark as all of you."
"That's a shame." He said, taking her hand and turning it over, kissing it lightly as was customary of purebloods. "It's a pleasure to meet you, though."
"It's a pleasure to meet you too, Brook. What do you think happened?" She asked, still smiling.
"I'm not quite sure. I was sitting down to eat with my friends, talking about some charms work that we were doing, then all of a sudden my friends were gone and different people were in their place. They all seem like good people though, and they have the same stories as me. Even more strange, they all seem to be Ravenclaws like me but I've certainly never seen them before." He said, seeming vaguely confused yet excited. "Maybe someone cast a spell to make people swap places with someone from a different timeline or reality? I'll have to read up on translocation magic."
"That sounds like a good guess. Let me know when you're done with whatever book you find, I'd like to read it myself. I've always been interested in obscure magic." Luna said as she turned back to her breakfast.
While the majority of students were handling their new situation quite well, at the staff table tensions were high and a fight seemed to be about to break out.
"I have known Albus Dumbledore for nearly my entire life, and while you may be old you're certainly not him!" McGonagall spat towards the man sitting next to her, wand trained on him.
Said old man had raised his hands lightly showing that he was not reaching for any want, and was smiling faintly though he had a steely glint in his eyes. "I assure you madam, I am. Yet I find that you, yourself, are not who you claim to be. I taught Minerva McGonagall you see, and while you appear to be about her age and have her fashion sense, there is sincere doubt in my mind that you are her."
Seeing as the old man sitting in the Headmaster's seat had made no hostile moves, McGonagall lowered her wand, just slightly. "I have lived my entire life being me, I think I'd know who I am."
"I'm not saying that you don't madam, only that you cannot be who you claim to be. Though there is one way to put this to a test, I suppose. Minerva is an animagus and has a form that I'm quite familiar with, having taught her myself. If you were to transform into said form I would believe you are who you claim to be." He said with a frozen smile.
"And leave you without a wand pointing at you and your merry friends sitting around me? I think not. I may not know what you have done with my fellows but I'll be damned before I let you do it to me." She snarled, pointing her wand back to the face of this wizard.
The other staff members sitting at the table were staring, quite confused, at the display before them. All but one of them, that is.
Snape sat still with a small smile on his face as he watched Minerva tear into Albus. He didn't know what had happened, but he had felt an odd sort of magic attempt to push its way past his mental barriers, failing miserably of course. He knew who each and every one of those in the hall was still, though nobody else seemed to.
Not that he was inclined to help either of the two at the table for the moment. This was far too amusing, and with what Albus had been asking of him this year, he felt that he deserved at least this.
Snape simply continued to eat slowly, watching the show.
AN: And so the prank finally occurs. What problems shall nobody being able to remember who each other is cause? I've always felt that the stories in which a "prank" was done were missing something. I mean sure turning people different colors might be amusing, but it hardly counts as a prank!