Sirius sat behind Krystal, so he could stare at the back of her head without her noticing. He had never paid much attention to her before. In first year, she had been "Remus' Smart Friend". In second year, she had become "Avery's Sister", and the association had never left. Avery practically killed him every time he flirted with her; he would have been pulp if he had ever said anything flirty to Krystal. Instead, he had just smiled and nodded and ignored.
Since he had "permission", he started to think about her. She was on the shorter side of medium, with wavy brown hair and clear blue eyes. She was always friendly, smart (but didn't rub it in), perky, and smiling. She was a little naïve, maybe (Peter had liked her for a year or two, but she had never noticed). She was definitely a quidditch fan; every game day, she dyed her hair red and gold. They made her Seeker that year, didn't they? She looked up to the Marauders (him especially? Maybe. Darn it, he should have paid attention) and stayed friends with Remus even after she had figured out he was a werewolf (three years before anyone else).
Sirius decided that she was okay. Krystal was not like Avery, but that was fine. As much as he liked her, Avery scared him a bit (and she had a boyfriend who was a Ravenclaw. She had chosen a NERD over him. Would she have chosen the nerd if she had known Sirius liked her? Well, she had to know. He only flirted with her every day. Well, she probably didn't know. He flirted with every girl. Besides, if she knew, she would say, "I hate you" right to his face. Oh, he hoped that would never happened. He wasn't scared of her because she threatened him. He was scared of her because one day she would find out he liked her and she would tell him she didn't care, because she liked that nerd she met in third year that she only dated to win the prank).
While he was thinking thus, Avery jabbed him in the side. "Hey!" he protested.
"Stop staring at Krystal like that," Avery hissed.
"I stare at all girls like that," Sirius pointed out. Honestly, though, he hadn't been staring at Krystal like that. He had been lost in thought about his inner turmoil, but of course, he could never tell Avery that.
"Well, Krystal isn't all girls!" Avery snarled. "Knock it off."
"I've been too scared before to look at her," Sirius truthfully replied. "I've never really seen her before."
"You better not break her heart," Avery warned. "Or I will rip yours out and feed it to the alligators."
"They were crocodiles," Catherine whispered from behind them.
"What?" Avery demanded.
"Indiana Jones and the Temple of Doom, right?" Catherine inquired. "They were crocodiles. That's the wrong side of the world for alligators."
"I don't care!" Avery muttered, visibly trying not to raise her voice. "I will feed his to the alligators. I don't have any rope bridges to break."
"What?" Sirius inquired, forgetting he was supposed to whisper.
"Five points from Gryffindor," Professor Kettleburn declared.
Krystal giggled, completely unaware of their conversation.
Not much to say here. Avery and Sirius kind of like each other, but Avery has decided make him date Krystal (who is still hopelessly infatuated with him). It's not until after the prom that Krystal realizes she would probably be better off with Remus, but by then, it's mostly too late.