A/N: This fan fiction was inspired by an idea from a tumblr post by siriestrange, fuckyeahdeathlyhallows, thatgirlonstage, and elidyce. I saw the 'what if' in it and said, 'Oh, let's make a fanfic out of it!' So here it is. When I revealed I was writing this, I had a surprising amount of interest in the story. I hope everyone is pleased with it, I am certainly having fun writing it!

In the original post, this was what I took as a prompt for a story:

From thatgirlonstage: 'Can you imagine how differently their lives would have gone if Ron, in trying to transfigure Scabbers, had actually transfigured him back into a human?

Just take a moment to imagine McGonagall's reaction if Peter Pettigrew had abruptly appeared in her classroom from Ronald Weasley's rat. Take a moment.'

From elidyce: 'Or if Ron had [m]ucked it up a little worse and couldn't get 'Scabbers' back and McGonagall had to take him to disenchant him and next thing we know there's a naked Peter Pettigrew sitting on McGonagall's desk and the kids in that class learn six new swear words, a hex they will never dare to use, and a fear of Minerva McGonagall's wrath that will be with them until the day they die.'

Obviously, I'm not basing everything in the story off this post. Just the general idea, the 'what if this had happened'. Also, as someone else on the same fan page later pointed out, this is based off events from the movie, not the book, because in the book everyone used beetles to learn this particular spell. So here is chapter one, and I hope everyone enjoys it!

Chapter 1: Transfiguration Class

It was just another normal day of school for the students of Hogwarts School for Witchcraft and Wizardry.

On this particular day, Professor Minerva McGonagall was teaching a class of second year students in Transfiguration. They were learning the 'Vera Verto' spell that transformed an animal into a water goblet.

As usual, Hermione Granger, a Gryffindor muggleborn student was the first to successfully transfigure her animal into a perfect goblet. Other students, however, were not having quite as much luck. Ronald Weasley's rat seemed to be stuck in a cross between rat and goblet.

The unfortunate animal was the shape of a goblet, but retained all the characteristics of a rat and was now squealing madly. Professor McGonagall sighed heavily and made her way over to the desk.

"Mr. Weasley, you must get something done about that wand," she said sternly. She picked up the rat-goblet and clicked her tongue disapprovingly.

"Yes, Professor," Weasley said dismally.

Professor McGonagall sat the rat-goblet back on the desk and tapped it, with the intention of undoing whatever botched attempt at 'Vera Verto' this was. The odd animal-like thing shook and squeaked, but nothing happened.

The professor pursed her lips. Something was off; this should not be happening because of a malfunctioning wand.

"Weasley, you're quite certain you used the correct spell?" she asked.

"Yes, Professor, 'Vera Verto,' like you said," replied Weasley nervously. He exchanged a glance with Potter and Granger and suddenly things seemed as though they were about to get much more complicated.

Professor McGonagall tapped the misshapen animal again and received the same response as before. She tried multiple charms and transfiguration spells, none of which had any effect. Finally, the transfiguration professor used a series of spells on the stuck animal, and something odd began to happen.

The goblet turned back into a rat, but then the rat rose off the desk and began to squeal. The rat grew and stretched, changing shape and losing fur. Within seconds, a small, balding, rat-like man was standing, quivering before the class.

Everyone gasped, including Professor McGonagall. She trained her wand on the man with a look so vicious many of the students shrank back into their seats.

"Oh… Oh my heavens," Professor McGonagall breathed. "You are supposed to be dead. This is impossible! Oh, Merlin!"

"P-Professor M-McG-Gonagall! How w-wonderful to s-see you again!" the man stuttered.

"Don't you dare!" Professor McGonagall said sharply. "You have no right to speak to me or any of these students until everything is settled."

The man whimpered, then began to look frantically around the room. When he made signs of moving, Professor McGonagall shot a red jet of light at him and he fell motionless to the floor.

At this, some of the students gasped while others screamed. The classroom had fallen into chaos. All at once, questions were flying from every direction.

"He wasn't really a rat?!"

"Who is he?"

"Professor, what is going on?"

"Why did you think he was dead?"

"Is he dead now?"

Professor McGonagall shot two red sparks into the air, sending everyone into silence.

"I will answer questions one at a time, in the order that I heard them. First, no, he most obviously was not a rat, but instead he is an Animagus, and an unregistered one at that. Second, I do not believe it is important that all of you know who he is at this moment, but I am certain that you will find out soon enough. Third, I myself am not certain what is going on, but I am sure the Headmaster will be able to sort it out. I, as well as the rest of the Wizarding world, believed him to be dead because of a terrible incident eleven years ago in which many muggles were killed, and all they could find of this man was his finger. Everyone assumed the curse was so powerful that he was completely obliterated, but as you can see, he was not, and instead is missing that finger. It appears that he faked his death for some reason. And no, Mr. Finnegan, he is not dead now.

"I want none of you to repeat this to anyone, not even your parents. Let the Headmaster take care of it. For now, you're dismissed and I want you to head straight to your dormitories until your next class."

Professor McGonagall whirled her wand above her head and whispered something, and a smoky looking cat ran off.

As Harry, Ron, and Hermione were packing up, Professor McGonagall stopped them.

"You three, come with me."

She levitated the unconscious man through the door into her office and the three young Gryffindors followed her. She bent down behind her desk and began talking into the fire.

"Albus, this is very strange. I think there may have been a rather awful mistake made eleven years ago."

Dumbledore sighed. "Step through, Minerva. We will get to the bottom of it. I will floo Severus as well."

Professor McGonagall nodded and stood. She motioned for her students to step forward and one by one sent them through to the Headmaster's office. Next, she sent the unconscious man on the floor, then she herself stepped through.

Dumbledore was staring pensively at the man who had just been pushed through his floo.

"Minerva, my dear, I believe you are correct; there has been a very grave mistake made."

"Sorry, Professor," said Ron, "but who is he? Why was he pretending to be my rat for so long?"

Dumbledore gave Ron a grim smile.

"Well, Mr. Weasley, why don't we bring Professor Snape in and find out for certain?"

"Yes, sir," said Ron.

Dumbledore walked over to his fireplace and threw some floo powder into it. Calling out "Severus Snape's office," he stuck his head into the fire.

"Ah, Severus! If you are not too busy, I need your assistance with a most delicate matter."

Snape sighed. "What is it?"

"Just bring a vial of Veritaserum. You would not believe me if I told you over the floo. I daresay you would call me mad."

Professor Snape snorted. "What do you need Veritaserum for?"

"It will become apparent the moment you step through."

Again, Snape huffed, but mumbled an "All right," and Dumbledore withdrew from the fire. A few minutes later, Professor Snape stepped through, holding a vial of clear liquid. His eyes widened when he saw the man lying on the floor, he looked at Dumbledore for confirmation.

The old wizard nodded and conjured a chair, then levitated the man into it. Professor Snape then conjured ropes to secure him to the chair.

"You might want to charm those ropes, Severus," suggested McGonagall. When she was met with an inquiring gaze, she elaborated. "He's an unregistered Animagus."

Snape nodded and tapped the ropes with his wand, and they seemed to grow slightly with the strength of the new enchantment.

"You three might want to go sit down," McGonagall said to her students. She conjured chairs for them along the wall of the office and gestured for them to sit down.

"Why are they even here?" Snape sneered.

"He has been posing as the Weasley family's pet rat for the past eleven years," said Dumbledore, giving Snape a pointed look. "Mr. Weasley is here because he has every right to know who this is and what the truth it, as do Mr. Potter and Miss Granger, as his closest friends."

Snape pursed his lips but said no more.

"I'll revive him," offered McGonagall. "Rennervate!"

The man in the chair was gasping and coughing as though cold water had been thrown on him. He looked around wildly, and after realizing the predicament he was in, he began to shake and whimper.

"S-Severus! H-Headm-master! P-Please!" the man whimpered.

Snape's lip curled and he roughly grabbed the man's face, forcing the Veritaserum into his mouth and down his throat.

Several seconds passed and the man's whimpering stopped. His eyes glazed over and he stared straight ahead.

"What is your name?" Dumbledore asked.

"Peter Pettigrew," the man answered.

The headmaster shared a look with his transfiguration and potions professors.

"Where have you been for the past eleven years?" questioned Dumbledore.

"Hiding with the Weasley family as their pet rat," Pettigrew answered in a flat voice.

"You are an unregistered Animagus?" Dumbledore supplied.

"Yes. I take the form of a rat," Pettigrew confirmed.

"Did you fake your death on purpose?"

"Yes. I cut off my finger, turned into a rat, and ran into the sewer."

"And before that?"

"I blew up the street. Sirius came to find me after what I did, he probably wanted to kill me, and he started chasing me. So I screamed to everyone that could hear that he did it, then I blew up the street. Then I cut my finger off. He couldn't catch me."

Dumbledore shared a nervous glance with McGonagall and Snape and nodded at the three students across the room. Professor McGonagall gestured for them to follow her out of the office – they did not need to hear what would come next. Not this way, at least.

"Wait out here," she instructed, closing the door to the headmaster's office behind them.

"What did you do to anger Sirius Black so much?" asked Dumbledore when the door had shut.

"I told the Dark Lord where to find James and Lily," Pettigrew answered.

"How could you have done so if you were not their Secret Keeper?" asked Dumbledore, confused.

"They switched at the last minute," he said. "Everyone felt Sirius was too obvious because of how close he and James were."

"You were the Potters' Secret Keeper?"

"Yes."

"And Black was angry because you sent Voldemort to his downfall?"

"No, he was angry because I betrayed Lily and James. He thought they would be safer if I was Secret Keeper, I was the least obvious choice, but the were all wrong."

Dumbledore paused for a moment. He shared a look with his colleagues, and then continued with his interrogation.

"You are a Death Eater?"

"Yes."

"Why did you fake your death?"

"Because either way someone would want me dead. Remus and Sirius wanted to avenge James and Lily. The Death Eaters that didn't go to Azkaban would want to avenge the Dark Lord. It was easier if they thought Sirius killed me."

Dumbledore nodded.

"The Veritaserum should be wearing off soon, Headmaster," Snape warned.

"Thank you, Severus," said Dumbledore. "Peter, why did you bring Voldemort to the Potters? Why did you join him in the first place? James and Lily loved you."

"I was afraid, and he was powerful. I didn't feel valuable to my friends. I wanted to be useful to someone or something, and the Dark Lord made me feel needed, important."

Dumbledore sighed and shook his head.

Pettigrew began to blink rapidly and looked tearfully up at the Headmaster; the Veritaserum had worn off.

"P-Please, Headmaster!" he begged. "P-Please don't let them kill me! Please help me!"

Dumbledore sat down at his desk and placed his hand to his forehead.

"The problem is, Peter, I can't help. You sentenced two innocent people to death and orphaned a young boy. That same boy was nearly killed that night, but by a miracle he is still alive. You also killed twelve Muggles who were merely innocent bystanders, and then allowed another man to take your place in prison. If at any time you felt overwhelmed in the past, you could have come to me for help and I would have gladly advised you and protected you. But you have made unwise decisions and acted on them, and now you must pay the price."

At this, Pettigrew began sobbing noisily, and Snape, thoroughly disgusted by this display, silenced him.

McGonagall let Harry, Ron, and Hermione back into the office.

"It is fortunate that Professor McGonagall assumed this malfunction was due to a wand error, Mr. Weasley," Dumbledore said. "Now a great justice may be served and an innocent man may reclaim his life. I will write to your parents and request that they come speak to me about this."

"Oh, Professor, you don't have to –" said Ron.

"I will make certain that your mother understands that you are not in trouble, Ronald, and that it was instead quite a shocking ordeal for you," said Dumbledore, peering at Ron over his half-moon spectacles.

"Yes, sir," said Ron, his ears turning red.

"Now, Professor McGonagall, if you could please see that these three get to their next class safely, I would be very grateful. Professor Snape, I only need to borrow you for a few more minutes while I do something about our unexpected guest and then I have a great deal of letters to write."

Professor McGonagall nodded and turned to the office door.

"Come along, you three."

The three young Gryffindors trailed behind her down the staircase.

"Professor," Harry said, "what's going to happen now, to that man?"

Professor McGonagall sighed and turned to face her students.

"I don't know, Potter," she said. "I'm sure we'll find out in a few days."

"Who was he talking about when he mentioned someone named 'Sirius'?" asked Hermione.

"I am not the person to answer that question, Miss Granger," said Professor McGonagall sternly. "I am sure all will come to light in a few days. Now hurry to your class."

Professor McGonagall turned on her heel and headed back toward her office.

A/N: Okay, so that was chapter one. I hope to put chapter 2 up tomorrow, and chapter 3 by New Year's, but I won't promise anything. I will say that they'll be up within a week. :) It won't always be like this, though, because right now I'm on break from school, so I have a ton of free time.

I have already had some suggestions for characters that readers would like to see throughout this story. Some characters I can confirm will make a permanent appearance in the story are Remus and Sirius. Who else would you like to see? What would you like to see happen with Remus and Sirius? Let me know in the comments!

Thanks for reading, everyone!

JHR