Disclaimer: J.K. Rowling is the reason this exists. I own nothing.
Part One – No, Potter.
"So. Sirius and McKinnon ay?"
Lily tore her eyes away from her book to look over at James. He had plonked himself down next to her on the couch by the fire and when she looked at him he nodded towards the corner where Sirius and Marlene were sitting, very close to each other.
"That's funny, I distinctly remember telling you not to interrupt me when I'm reading at least, hmm, five times in the past week alone, Potter."
"You know what else is funny? Sirius and McKinnon," James said, ignoring the clearly uninterested look in Lily's eyes. He was used to it.
"Hilarious, now would you please go away?" She deadpanned, but James seemed not to notice.
"They're an unlikely couple aren't they? Who could have picked they'd end up together? I certainly didn't. But you can't stop true love like that. It's just—"
"I give them one more day at the most," Lily interrupted bluntly.
"Wh … huh?" James faltered. "You don't believe two people can overcome their differences and fall in love?"
"Oh no, I definitely think that's possible, just not for Sirius and Marlene," Lily replied simply.
"But why not?" James demanded.
"Well, for one thing Marlene only agreed because she was curious to find out if Sirius's snogging was worth the hype. And something tells me Sirius is only dating her because she's the best-looking Gryffindor in our year. I think he just thought it was inevitable at some point."
James opened his mouth to argue, but realised Lily was right and shut it again.
"But you do believe two people can overcome their differences and fall in love," he said.
"No, Potter," Lily said with a sigh.
"No, you don't believe that—"
"No, I won't go out with you."
"But I wasn't going to—"
Lily raised her eyebrows at him.
"I hate when you're right, Evans," James muttered to himself, getting up and joining Remus and Peter in the corner.
Lily watched him with a satisfied smirk, before returning to her book.