Gryffindor Scarves.
"Regulus, why do you have a red scarf on?” Regulus glanced up from the book he was reading. “Because, Barty, it’s very comfortable.” Barty rolled his eyes before slumping down on the couch next to Regulus. “Yes, yes, I get that. What I mean is, why do you have it?"
Regulus took a moment before flipping a page in his book. “Do I have to remind you of the fact that I have a brother in Gryffindor?" Regulus asked with a slightly deadpan voice. Barty gave a small huff and scooched closer to him before touching the scarf. “This is absolutely not Sirius’ scarf; no offense, Reggie, but wouldn’t he rather share his scarf with Mr. Future Prefect himself?” Regulus gave a small shrug before looking back at his book. “Believe what you want to believe, Barty."
Barty gave another huff before he walked off from Regulus. “You know what I’m going to ask Sirius himself" Regulus didn’t bother to respond.
"Now where does one go to find the elder of the black brothers?” Barty wondered aloud before he went to the library. On the way there, he heard a shout. “I am not going to sit here and study potions for more than 10 minutes!” And then he grinned, realizing who it was.
Barty walked into the library and immediately saw Sirius, Remus, James, and Peter sitting at a table. Sirius looked outraged at the idea of studying potions, while James and Peter looked amused, and Remus just looked fed up. “Mister Black? I do hope I’m not interrupting anything too important."Barty asked, pulling up a chair as he sat down at their table.
Sirius looked distrustfully at him, as did Peter, before Remus spoke. "No, you’re not; Sirius just has an issue with potions.” He said it tiredly. Barty nodded while looking slightly amused. "Right, well, still. But as for the reason why I’m here, I just saw Regulus in the common room with a gryffindor scarf; now that may not be a cause for concern in and of itself-" Sirius fake coughed “Get to the point, Crouch,” Barty, rolled his eyes. "Right, as I was saying, I then asked him where he got the scarf from, and he said he got it from you."
Sirius looked confused, as did the rest of the table. “I never gave him my scarf." Sirius muttered, confused. “That’s why I didn't believe him, obviously. But thank you for that, Mr. Black. I just wanted to confirm.” Barty said before he slinked off and away.
“Who would give Regulus their scarf?” Peter asked Peter from his seat, looking at Sirius, and Sirius just shrugged. “I don’t know, but the fact that he’d use me as bait is just so... it’s a very him thing to do."
Remus shot a small, knowing glance at James. “Could Regulus be dating a gryffindor?” Sirius stared at him, slack-jawed. "Merlin's balls, Regulus could be dating a gryffindor.” Peter let out a small snicker at Sirius’ expression. While James was sitting in his chair, his foot was bouncing up and down, looking a bit nervous. “Couldn’t Regulus just have a Gryffindor friend?” Sirius had a funny look on his face. “Friends don’t just give each other their scarf to wear in their free time!" Remus had a small grin on his face. "Yeah, Prongs, friends don’t just do that." James shot him a small glare. “Don’t you and Sirius share your scarves?” Both Sirius and Remus stuttered a bit. “Th-that’s not the same, James!” “That’s different, and you know it, Prongs!"
James gave a small smirk. “Because that’s so different." Remus had a red tint to his face. “Regardless Prongs, we have to figure out who’s making moves on my baby brother!” Sirius said in a half shout, but then Madam Pince shushed him. “Either quiet down or get out, Mr. Black!” Sirius glared at her before gathering up his things, as did the rest of them, and on the way out, he muttered, “Old bitch, can’t even let me mourn my baby brother's loss of innocence." James blanched, and Remus smirked.
“So you think the gryffindor who gave Regulus their scarf also hooked up with him?” Sirius turned around and immediately looked aghast. "Moony! No, obviously not; I didn’t mean like that!” Remus snickered, as did Peter.
“So, how are we going to figure out who’s “taken” your brother's innocence?” Remus asked Sirius. Sirius looked a bit miffed over not having thought that far, and then he brightened up. “We’ll steal some veritaserum from Slughorn's office!” The three other boys looked at him like he was both brilliant and very dull.
“And after we’ve done that? We’ll just use it on everyone in Gryffindor." Asked Peter, and yet again, Sirius looked a bit miffed. “Well, alright, that might take too much time. So, we steal it, and then we test it on ourselves, and then we convince Regulus to drink some.” Sirius explained his new plan.
They all eventually agreed to it, even with both Peter and James looking nervous.
When they come to the common room with the potion, Sirius and Remus sit on the couch together, Peter sits on a chair, and James sits down on the floor next to the couch.
“So who wants to start us off?” Asks Sirius with a big grin; surprisingly, Peter takes a small sip and sits there fidgeting with his hands before Remus asks the first question. “So did you really do the transfiguration homework all on your own, or did you copy one of us?” Peter looks even more nervous as he tries to fight off the potions effect on him before he finally relents. "Fine, yeah, I did copy your homework.” Remus shot Peter a small shrug. “You could’ve just asked."
Sirius spoke up. "Okay, so we know it works. Now should we try someone else just to be sure, or is this good enough?" James was about to speak up before Remus did. “We could always try it on Prongs." James gave Remus the stink eye before he reached for the bottle. “Fine, fine, I’ll do it." And then he took a sip. Sirius was about to ask the question when Remus whispered something to Peter, and then Peter asked James, “Did you give Regulus your scarf?"
James shot Remus a slightly panicked look as he tried to keep his mouth shut before he couldn’t anymore. “Yes.” He said it as quickly as he could and avoided looking at Sirius. Sirius looked rather shocked. "So, are you dating him?” Peter asked quickly, and James outright glared at Peter, as did Sirius.
“I am.” James said quickly before getting up from the floor and trying to escape, but Sirius had already tackled James to the floor.
Remus and Peter were watching before Peter looked at Remus. “Should we help him?” Remus shook his head. “Nope, he brought this on himself."