Disclaimer: None of these characters are mine.
"EXPECTO PATRONUM!" Even with his eyes shut in concentration, George felt something very different about the spell exploding from his wand. He peaked from just behind his eyelids at it as it began marching determinedly toward the dementor. It was much bigger than his fox had been, and it was reared up on its hind legs like an angry bear, but from as far away as it was, George couldn't make out what it had become. But then he heard something he thought he'd never hear again.
"BOO! You ugly, scabby git! Leave my brother alone!" George's eyes widened; his mouth fell agape. A silvery, shimmering Fred Weasley stood in front of the dementor, laughing wickedly and making rude gestures at its quickly retreating back. Blindly, George ran forward until he was mere inches from the Patronus he had just conjured, afraid to trust his eyes. Fred turned to look at him and grinned. "Surprised to see me, Georgie?" A faint, disbelieving smile hinted at the corner of his mouth.
"Fred…you…you're…?"
"Your new Patronus."
There was a pause as George seemed to be unable to digest this. "Personally, I think it's quite the handsome improvement from that mangy ol' fox, don't you think?" Fred said, foolishly tossing his hair and beaming at him cheekily. George smirked.
"Yours was a fox, too, you know."
"A vixen, thank you very much. Seeing as I was always the one to attract all the ladies."
George would've rolled his eyes if he wasn't still so amazed to see his brother standing before him. He was still temped to think he'd finally lost his mind to grief.
"But…I didn't know Patronuses–"
"Patroni."
George scowled at Fred's know-it-all smirk. "As I was saying, I didn't know Patroni could be…humans." Fred shrugged. Obviously, he didn't, either, so George continued, "or that they could talk. I mean, not like…not like you're talking. I thought only Priori Incantatem could do that." At that, Fred's smile seemed to split all the way across his face.
"I'll let you in on a secret, your Holeyness." Fred whispered excitedly, "I'll bet you a thousand Galleons I'm the only one who can. But, I mean, how else am I supposed to scare dementors away? I'm about half their height and I don't have any horns or sharp teeth or claws or anything. You put me up to quite a job, you did."
"I didn't mean to." George mumbled, suddenly feeling guilty. Fred waved his hand dismissively, his expression playful. "So…for good, then?" George asked after a moment, and Fred didn't even have to ask what he meant.
"Looks like you're stuck with me, bro." He answered, and then winked, "Like you could get rid of me that easy." George laughed. After so long since he had, the laugh felt odd in his throat and came out sounding slightly croaky. Fred's smile widened even further. "There you go! It's been quite a while since you've dared do that, hasn't it?" George bit his lip, looking guilty again.
Fred let out a loud sigh and said, sounding alarmingly like their mother, "Look. Not that I don't find it highly flattering that all of your Patronus memories since I've died have been of me–" at this, George blushed and glanced to his left. He didn't think Fred would be able to tell what memories summoned the Patronus, especially if up until just now, it hadn't even been him, but he supposed, being his brother, he probably could've guessed. "–but don't be afraid to be happy, okay? You can make new memories. I won't take it personally." George felt tears sting at his eyes, but forced them back. He nodded, his throat feeling too tight to try and speak.
Fred gave him a sad smile. He leaned forward and kissed his forehead, which felt to George like leaning against a warm glass window. '"Make me proud, George." Fred whispered, and looking him in the face he winked again, "I'll always be here for you."
With that, he vanished, transforming into a glowing silver mist that seeped back into George's wand. George blinked, the tears he'd held back earlier now spilling down his cheeks–though he wasn't sure now if they were from sadness or joy. He looked down at his wand and smiled, giving the handle a small squeeze before putting it gently back into his pocket.
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A/N: Okay, so I really have no idea if a human can be a patronus, and honestly I don't care. George needs his twin. D: Written and loaded in fifteen minutes, so forgive little mistakes. Oh, and the dementor. ...yeah, I dunno where it came from. Maybe it was a rogue one from Azkaban.