Summary: Remus is having a very bad day. When the cauldron explodes…well, everything else does too along with it. It was all James fault, really. It almost always is. Sirius/Remus

Disclaimer: I do not own anything. But boy, if I did…

A/N: I was planning for this to be a one-shot. Apparently, that was impossible and now this fic is completely out of control. The rating might change in the following chapter(s), I'm not sure yet. The idea belongs to Blue Skyes101 who left me this prompt in the 'Request Challenges' Harry Potter Forum:

Sirius/Remus Through some freak magical accident, maybe in Potion's class, Sirius and Remus switch bodies. They then learn their true feelings for each other. You could even expose some Slytherin friendships that the two have or go into Sirius and Regulus' relationship.

Quotes:

"Wait, does that mean I'm wearing your underwear?"

"Great, now I'm short."

"You mean you don't hate me?"

"So I'm a werewolf now? Do I get to join an exclusive club?"

Prompts:

Pineapple

Linen

Dog Bone

Wand

Lamp

This first part was written a bit hurriedly and it's unbeta'd. If there's anyone willing to help me with all the atrocious mistakes, you're welcome to do so! Enjoy…

xxx

Contrary to popular belief, James Potter is not an idiot. Sure, everyone knows, from the Professors to the slimy wannabes in first year in Slytherin, that he's a brilliant student. However, everybody somehow neglects or simply misses the fact that James is also a very intelligent person when it comes to something other than school subjects and talent in magic. He's quite perceptive, actually, when it comes to people and relationships.

That's why he knew right away that Sirius would be his best friend in the world, why he feels his hatred for Snape is reasonable and why Lily Evans and him will end up married some day in the—hopefully not so distant—future. She'll come around eventually he reckons (since they're destined to be together), she just needs a bit more time; not everyone can see such a blinding truth as clearly as him. That's also why he knows, before everybody else has figured it out, that Sirius may not be in fact as straight as all girls wish he were and that Remus is definitely interested in personally finding out if the above statement is true.

However, as mentioned above, James is not an idiot. Just because he happens to know these things for a fact doesn't mean he'll actually do something about it. Yet.

It turns out, eventually, that being the seventeen year-old boys they are, after a little while James starts getting tired as suddenly pranks and general mischief are not enough to vent all the pent up frustration hormones can cause. He promises himself he won't allow his brain to form any plans to force Sirius and Remus face their—uh! he hates that bloody word—'feelings' and get on with it so he can continue with his efforts of seducing Evans in peace.

He actually manages to hold back for two whole weeks before he breaks and he starts forming a very wicked, very promising and very entertaining (for him and Peter, not Remus and Sirius, let's not be daft here) plan in his head. It's a true masterpiece, one of his very brightest ideas and he feels ridiculously proud of himself for having thought of it.

Of course, it all then goes to waste because Slughorn has to go and pair him off for the first time in all five and a half years he has been at Hogwarts with one Lily Evans. And reluctant or not, he figures, Lily will have to make at least some kind of conversation with him and James, the poor, lovestruck bloke that he is, could not ever possibly divert his attention completely from her. In retrospect, it may had been a wise move to tell Peter about the plan and allowed him to help, but at the moment it had seemed unnecessary and kind of risky considering Pete's reputation and history with Potions.

In any case, James's plan to enhance the undoubtedly perfect Veritaserum Sirius and Remus would produce in order for the vapour to slightly affect them, backfires like a broken wand in a duel.

In his defence, Lily had been smiling at him.

xxx

Remus's day hadn't been a good one so far. Between a second year Hufflepuff accidentally dumping his breakfast on him, Peter staining his Transfiguration essay with bacon grease and getting stuck for fifteen minutes on a staircase Peeves had somehow blocked…well, his patience had started running thin. The fact that he had lost a bet the previous evening and had now an afternoon playing fetch with Padfoot to look forward to didn't exactly help. Now, of course, Remus loved Padfoot, sometimes he was even more bearable than Sirius himself, but with the full moon less than a week away, the thought alone of what was waiting for him made his knees weak.

Potions was a subject he was never really good at and Slughorn pairing him off with Sirius seemed like the brightest moment of his day so far. Sirius was really good at Potions. Basically, Sirius was good at everything—from Charms to Arithmacy and from Quidditch to being annoying. Like right now for example.

"You're lucky, Moonbeam," he whispered, "my heart cries for all your lost cauldrons to this day, but today…today you're honoured to be paired with the best in this class."

"You're excellent at Potions, Sirius, but you're not the best," Remus hissed through clenched teeth. "And stop with that nickname, it's de-"

"WHAT?"

"Shh! Keep your voice down!"

"What?" Sirius whispered loudly this time, "I'm not the best in Potions?"

"Oh come on, everyone knows that S-"

"Chop that, will you?" Sirius interrupted him. "And try to make the pieces even this time, okay?" he said offhandedly and Remus simply rolled his eyes because, honestly, Sirius could be such a child sometimes. An adorable one at that.

"I was going to say that Lily is the best one."

"You were going to say 'Snivellus' and don't you try and deny it! I will not tolerate this, Remus. No friend of mine is allowed to talk like that about him."

"Actually, you're wrong, Padfoot," Remus smirked, "I was going to say 'Snape'."

Remus knew he was being cruel on purpose, but he enjoyed immensely rising Sirius's temper in class and watching him while he tried to control it. His face would always turn a lovely, but kind of disturbing purple shade and a vein would pulse rhythmically on his left temple.

Remus just kept smirking.

"What is Prongs doing?" Sirius asked in an obviously desperate attempt to change the subject. However, when Remus turned his head to glance towards James and Lily's direction, he did note that the former was showing a surprising lack of interest in what the later was saying. "I imagined he would pee himself from his excitement to be within touching distance of Evans," Sirius commented thoughtfully.

"Hm…Maybe he finally had enough of Lily's lecturing? Who knows wh- Sirius! Watch out, will you?" Remus almost cried as the bottle containing four rather fragile Jobberknoll Feathers crashed on the floor.

"What? I didn't even touch it!"

"Okay, let's focus on the Potion and leave James and his weird behaviour in peace for now, okay?"

"Alright, mate, calm down…Hey, is the potion supposed to do th-"

BOOM

The saddest part was that Remus wasn't even surprised. The explosion was not the worst in Remus's long history of explosions, but the smell of the spilt potion was extremely disgusting and he didn't think he had ever felt a stronger need for fresh air. He could hear Sirius almost gagging.

"I think not…" Remus said in a thick voice as a light pink, gooey substance dripped from his hair to his face.

"But, we didn't do anything wrong!" Sirius almost managed to pout as he tried to peer into the cauldron that was completely covered in thick white fumes, plugging his nose with his fingers.

"Mr. Lupin, Mr. Black, what on earth have you done, my dear boys?" Slughorn's worried voice came as he manoeuvred between the desks, trying to reach theirs. "Are you alright?"

"Uh, yeah, yes, I think we're fine," Remus said while trying to remove the remains of the failed potion from his eyes.

"I think pink is quite your colour, Remus, it compliments your hair," Sirius chuckled right before he tried to turn towards James, probably in order to share the joke, but as fortune would have it, he slipped on the potion that was covering the floor and crashed squarely on Remus himself.

And that was precisely the moment everything took a turn for the crazy…and that says a lot when you've spent five years sleeping next to James Potter and Sirius Black.

"I-" Remus begun, once he detached Sirius's limbs from himself and helped him regain his balance, but his voice sounded wrong so he cleared his throat and tried again, "I-I think, uh...there's something wrong."

"You think?" Sirius deadpanned after a few seconds of watching him. "Your face looks like it's melting," he said.

"I think you should visit Madam Pomfrey immediately," Slughorn said, looking sceptical-a true sign that something had indeed gone terribly wrong, "and someone should probably call Professor McGonagall. I'll be there as soon as the class is dismissed, in about twenty minutes."

The ones who offered to help Sirius and Remus to the Infirmary and make sure McGonagall was notified, were James and Peter of course. The fact that James was not howling with laughter by that time, distressed Remus more than anything else really.

The walk to the Infirmary was unusually quiet and Remus was not even surprised. If Sirius was experiencing half of the things Remus was, he couldn't imagine him wanting to talk for any reason.

There was something very strange happening to his body. He couldn't exactly pinpoint the source of his discomfort, but he just didn't feel right in his own skin. There was a tingling sensation around his muscles that reached right to his bones and cut through them; not exactly painful, but not pleasant either. He felt like scratching his arms and legs and back as if there was an unidentifiable itch. He wanted to shake his hair out of his face, brush them aside, but that was completely ridiculous. He had never had long enough hair to do this.

"Merlin's beard!" James exclaimed and Remus whipped around, not being used to James sounding so distressed and he almost fell over his own feet.

"Wow, watch it, er…Remus," Peter said when he managed to catch him. His eyes were huge and he was definitely staring. Remus didn't comment on it, he just threw James a curious glance silently asking what on earth had happened, but James ignored him, so he just kept walking straight ahead, hoping there wouldn't be any more accidents.

Peter soon left them to head to the Transfiguration classroom and the three boys quickly reached their destinations with no accidents happening. For once the Infirmary was completely empty and Madam Pomfrey heard them entering right away and she rushed to see what was the problem with them this time. The look she gave them as soon as she was close enough to inspect them was not unexpected, especially considering their record of accidents and injuries. What was unexpected was the stern look she threw at Remus before speaking. He had honestly thought she kind of had a soft spot for him.

"What have you done this time Mr. Black?" she asked him and Remus just stared at her.

"What? I'm not-" he tried to say because apparently, after five years of taking care of him, she had somehow forgotten his name. "This is Si-" and that's how far into the sentence Remus managed to go before he lost all ability of speech because as soon as he turned to indicate Sirius, the English language failed him.

"What." he managed to say at last, not able to take his eyes off of- well, his eyes.

Because Remus was staring down at himself. Right in front of him was standing a complete and perfect duplicate of himself; and he was staring down at it.

"Great," said the duplicate, "now I'm short."

"What." Remus repeated unintelligently and this time he noted that he didn't recognise the voice that came from his throat at all. He lifted his hands slowly and he took in a sharp breath when the hands that came into view were not his own, but a pair he knew almost just as well. "Oh my God."

"Is that what I sound like? Really?" Sirius said in Remus's voice and it was very much disconcerting how unfazed he was by the whole thing. "I thought my voice was deeper…"

Remus turned sharply around and glared at James who had stayed a few feet behind and was trying to decide if it was a good moment to start laughing or not. "What did you do?"

"What? Nothing!" James exclaimed, managing to sound offended. Remus knew better.

"You're obviously feeling guilty James, otherwise you'd at least have made a dirty joke by now," Remus accused and Sirius seemed to agree with him as he turned questioning eyes on his best friend.

"Well…there might have been an- uh, accident…"

"Et tu, Brute?" Sirius asked incredulous in a pompous tone that really didn't bode well with Remus's voice.

"You mean to tell me you have somehow managed to switch bodies?" Madam Pomfrey sounded rather amazed and a sinking feeling settled somewhere in Remus's stomach.

"What is going on?" a very familiar voice called from the doors and before he had even turned around he knew the look on McGonagall's face would not be a pleasant one.

"Mr. Black and Mr. Lupin here, appear to have switched places in each other's body, Minerva."

"'Accident' in Potions, Professor," Sirius said and everybody could clearly hear the quotation marks around the first word.

McGonagall remained silent for a few seconds, observing them uncomfortably close and Remus tried very hard not to fidget. "I see. And whose fault was that?"

Three sets of eyes, all except Peter who had been with McGonagall when James made his half-arsed confession, turned to James.

"Of course," McGonagall commented idly, "who else. Detention tomorrow evening at eight o'clock in my office, Mr. Potter. I doubt this was really an accident."

James didn't see the point in complaining, probably used to this by years of personal experience, and soon afterwards, Madam Pomfrey took Sirius and him to give each a thorough examination to make sure nothing else was wrong. Thankfully, the potion didn't appear to have any other kind of effect on them and they wouldn't need to spend any time in the Hospital Wing at all.

When they came out to where James and Peter were waiting for them, Slughorn had already arrived and he was talking in hushed voices with McGonagall.

"Mr. Black, Mr. Lupin, please come here. I think there are a few things we should discuss," McGonagall said. "I'm assuming you're all familiar with Remus's condition?" she asked looking each and every one of them in the eye.

"Yes, of course," James said, "what does it have to do with anything?"

Remus didn't need McGonagall to explain herself because suddenly he understood fully what she was trying to say. Slughorn may be one of the greatest Potions Master, but even he couldn't guarantee how soon he'd be able to find an antidote. And if it took him more than a week, then Sirius…

"No!" Remus cried terrified. This couldn't happen, he wouldn't allow it to happen.

"I'm afraid, Remus, that unfortunately it's not really up to us," McGonagall said in a soft voice, her eyes sympathetic, and Remus hated this, he didn't care how sorry they felt, he didn't care how sympathetic they looked, they would never understand. He wouldn't ever allow Sirius to go through this.

"I promise I'll have the antidote ready as soon as possible," Slughorn said.

"Merlin's pants!" James shouted as realisation sank in and the guilt shown on his face almost made Remus forgive him.

"Wait," Sirius finally said in a grave voice, probably realising what was going to happen if Slughorn had any difficulty with the potion. "Does that mean I'm wearing your underwear?" Or probably not.

"Oh for Merlin's sake, Sirius…" Remus sighed.

"Cause that's kinky," Sirius went on smirking, completely unaware of the dark and dangerous possibilities his future might hold.

"Mr. Black, please do keep these thoughts to yourself," McGonagall shook her head. "In six days it's the full moon and if you don't have the potion by then you will be transforming in Remus's position. I'm sure that's something we would all like to avoid."

"I know, but it's okay," Sirius shrugged and Remus just stared at him. James chuckled and Peter squeaked a bit. Nobody—nobody, not even Sirius Black, should ever be allowed to feel so relaxed about the possibility of turning into a werewolf.

"No, Sirius, it's not okay, it's so far from okay, you'd have to Apparate on the Moon for it to be even remotely close to okay," Remus said in a sad voice.

"There's nothing you can do for now, though" Slughorn said, "so I'd suggest you try and keep your calm. Mr. Potter, would you mind accompanying me to my office? I need to know what exactly happened to that potion."

As James left with Slughorn and McGonagall, the three Marauders left headed to the Great Hall for dinner and ready to face the confusion that would follow when people would start noticing the differences.

Remus was almost one hundred percent sure that Sirius had already started thinking of new pranks he would best execute in his new form and he decided he didn't really want to know and he wouldn't ask if he didn't absolutely have to. As he walked towards the Gryffindor table, Remus tried very hard not to think of the alone time in a bathroom he would soon have to face, especially seeing as he was in a very public place, in a body that didn't belong to him.

xxx

TBC