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If ever asked who was the brains behind the Marauders pranks, the answer would never be Sirius Black. Sure he made good marks in class, but the boy lacked in the planning department. So when he came up with the amazing plan of using a polyjuice potion to turn into his brother and then flirt with his best friend and he kept this plan to himself, there was no one to tell him maybe it wasn’t the best idea. But he was certain that James was falling for Regulus and due to teasing from his fellow Slytherins he knew his brother liked him. Or at least he had back in third year. And sure maybe crushes can change in three whole years but Sirius was set on the idea that they’d fall in love with each other. It would have been so much easier for James to tell the truth when Sirius had asked him multiple times if he had a crush on Regulus and despite Sirius’ assurances that it would be okay, James always came back with a squirrelly answer. So now he would take matters into his own hand.
The plan was simple. Sirius had spent the past month brewing a polyjuice potion and had swiped the invisibility cloak earlier to grab a set of Regulus’ robes and his cologne. He downed the potion and studied himself in the mirror. It was eerie seeing a different face in the mirror, even if it was one he was so familiar with. He was hyper aware of all the subtle differences between himself and his brother. Sirius got dressed, he sprayed the cologne that honestly he might not give back to Regulus because it smelled really nice, and he did his best to style his hair in the same way his brother did which was more challenging than he would have thought. Finally he was ready and the plan could come to life. He rushed down to the hallway outside of McGonagall’s classroom and waited for James to get out of detention. He did his best to match his brother’s brooding mannerisms.
When James came out, he kept the same composure. He couldn’t make it obvious that he wasn’t Regulus. He hardly looked up but still immediately called out to James. “Hey, Potter.”
James smiled upon seeing him and Sirius was certain he was right. Although he didn’t have time to relish in how correct he was when James looked around and immediately pulled him into a nearby broom closet.
Sirius yelped as his best friend began snogging him. He pushed James away and James immediately took a step forward back towards him, examining his face with worry. “What’s wrong, love?”
Sirius had a lot of information to process from the last ten seconds and unfortunately it seemed to block any of it from actually entering his brain.
“What the fuck, James?”
“I’m sorry. I thought we agreed to assume that was always okay unless you said otherwise. Is everything okay? Did I do something wrong?” James was growing very worried.
“What the actual fuck, James?” Sirius repeated.
And something clicked in James’ brain. Regulus, not once, not even during a fight or drunken daze, had ever called him James. He took a step back, examining the Regulus look alike in front of him. His brain turned for an explanation before it stopped on “Sirius?”
“What the fuck was that?”
James buried his face in his hands. This was not how he wanted to have this conversation. Not after pushing his boyfriend’s brother, his best friend, against a wall and trying to shove his tongue down his throat. “No what the fuck is this?” He yelled, gesturing to Sirius.
“I was just going to flirt and get you to realise that you’re an idiot who is in love with my brother!” Sirius yelled.
“Well, I guess in a way, you got what you wanted,” James said with an awkward smile, trying to lighten the mood.
Sirius shoved him. “I wanted you to like my brother, not defile him in a broom closet!”
The door opened and there stood the real Regulus Black who had come up to see James and instead heard his boyfriend yelling in a closet with someone that sounded suspiciously like himself. He took in the scene with narrow eyes. “You’re a fucking idiot,” he told Sirius. “And I guess we aren’t hiding anymore.”
“I’m sorry, love. I know you wanted to wait to tell him.”
Regulus pulled James out of the closet by the tie. “It’s fine. At least now you can stay the night in my dorm.”
“Stay in your dorm?!” Sirius yelled. “He won’t be staying in your dorm! Prongs, I wanted you to fall in love, not corrupt my little brother.”
Peter and Remus grew worried when they entered the dorm to find Regulus looking distraught, sitting on Sirius’ bed.
“Reg?” Remus asked carefully.
“Not Reggie. I’m waiting for this fucking polyjuice potion to wear off so I can tell them off properly.”
“Of all the ways to find out,” Peter laughed.
“Did James try to snog you?” Remus asked, biting back a laugh of his own.
“You both knew?!”