A/N: Based on something from HBP. When Harry was copying down Filch's records for his detention, he came across one that stated the James and Sirius had received detention for hexing Bertram Aubrey, making his head twice its normal size. I thought this was a convenient way to give that a backstory. Enjoy!

Harry Potter Halloween Collection Prompts: (restriction) exactly 666 words long; (word) revolting

As soon as Sirius walked through the portrait hole with James, he knew something was wrong. Everything in the common room appeared normal; students were grouped together as usual, talking or studying, just like every other day, and bright sunlight spilled through the windows.

"Pads, look." James pointed to a corner of the common room. "Wonder what's got her so upset?"

Lily and Marlene sat together on the floor in that corner, Lily's arms around Marlene, Marlene's head buried in the other girl's shoulder. Sirius could hear Marlene sobbing. He brushed past James to investigate, his fists clenching. It made him angry to think that something had upset her so much as to make her cry like that. Whatever it was, he wanted to fix it.

Sirius didn't know Marlene that well, mostly because she was Lily's best friend and Lily tended to avoid James and his friends like they had a bad case of dragon pox. She wasn't hanging around that slimy git Snivellus anymore at least, but she still wanted nothing to do with James. Sirius had been watching Marlene since their first year and had recently developed a crush on her. James had been teasing him mercilessly about it, but Remus and Peter were having the most fun, pointing out the fact that James and Sirius were apparently so inseparable that they even fell for two girls who were just as attached to each other.

"What's wrong?" Sirius asked when he'd joined the two girls. He knelt down next to Marlene, placing a comforting hand on her arm.

"Bertram Aubrey," Lily said. Her worry for her friend was seemingly overriding her distaste for James and Sirius at the moment. "You know, that Ravenclaw she always hangs around with, her boyfriend. He just broke up with her."

"H-He said I w-was horribly u-ugly!" Marlene howled, still leaning on Lily. "And s-stupid and boring and revolting-"

"That's enough," Sirius said gruffly. Even Marlene ceased crying and looked up at him. "He's wrong. You know what's really revolting? The fact that he's such an idiot he can't see how lucky he is to have you." Sirius was so angry that he might've hexed the stupid git Aubrey if he was in front of him. I suppose that could be arranged...

"You...really think that?" She looked at him in disbelief, her eyes red from crying and her face tear-stained.

"Why would I lie to you? You deserve better than him. You're kind and funny, you're loads smarter than that idiot, and you're the most beautiful girl in this school." He tried to keep his face neutral and not panic. That last bit had just slipped out before he could stop it. The last thing he needed to do right then was tell her how he felt. It would be insensitive. He stood before she could say anything about it. "Come on, Prongs." He walked quickly towards the portrait hole.

"Where are we going?" James asked, nearly running to keep up with Sirius as they stepped out of the common room once more.

"We're going to find Aubrey and make him wish he'd never even laid eyes on Marlene. The only thing I need you to do is keep me from killing him." Sirius took out his wand. Which hex does that bastard deserve? Probably every one I can come up with.

James grinned as he followed his best friend. "Promise. Although I'd say he deserves it."

"Too true. But I doubt Marlene will be too happy if I kill him. I just need to make him regret making her cry."

Later that night, as he lay in bed, Sirius remembered Marlene's smile when she'd gotten a peek at Aubrey in the hospital wing, his head blown up to twice its normal size. He had done that. He had brought a smile to her face again, after that idiot had made her cry.

Making her happy was worth whatever nastiness Filch had in mind for his detention.