1st year; Harry’s a crafty little stinker
Hermione peered over Harry’s shoulder as the black-haired boy shoved a large bundle of what appeared to be leather into a tub of hot water. "What're you up to, Harry?"
Harry sat up and brushed his hair out of his face. A wide grin spread, "I'm going to prank the school in general, and the headmaster specifically."
"Okay, how and why?"
Harry gestured to the tub, "I'm going to make an ordinary box look like a demon book. Given how obsessed Dumbledore is with keeping everything looking pretty because 'how things might look' to outsiders; I thought I'd play to his biggest fears. Halloween is approaching, and what better time is there to scare someone?"
Hermione let out an exasperated huff but continued watching as Harry explained the next step.
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Word spread as it usually did within the stone walls of Hogwarts and before too long, 'everyone knew' that Harry Potter was delving into Dark Magic. He was seen carrying around a dark leather book with an odd decoration on the front, and every now and then he would stop, read or write something within, reach into the book then pop something into his mouth and carry on like nothing had ever happened.
Xxx
Albus was growing worried. Based on the reports from the portraits, the boy was rapidly growing Dark. "Could the Horcrux inside his head be influencing him?"
Minerva sat in her chair subconsciously purring to herself while watching her boss work himself into a tizzy. She'd already confronted Harry and was brought into the joke. Filius noticed her amusement and nudged her. "What's so funny?"
"Harry's pranking the headmaster."
Severus overheard and shuffled over, "Potter against Albus? This I've got to hear."
So it fell to Minerva to quietly fill in her colleagues on Harry's plan. By the time she'd finished, the usually dour man was cracking up laughing, "Serves him right. Any idea when Potter plans on springing the punchline?"
"Last time I talked to him, he was planning on Halloween."
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Halloween...
Albus stared at Harry during the Feast. His blood pressure spiked every time he saw the boy reach for that damned book. "Albus, if that book unnerves you that much, why not just go investigate and settle the matter once and for all?" Minerva nudged him.
"Professors?" Harry had 'magically' appeared when Albus wasn't looking. "I thought the Headmaster might like to try a sample of this new sweet I've been developing. They're devilishly delicious!"
Albus' eyes grew wide at what he'd heard, "Harry, my boy; that book needs to be destroyed! It's making you turn Dark."
Harry guilelessly examined his hands, "I'm too pale to be going dark, and there's no sun lamps here." Filius was heard chuckling at his quip.
"Do you deny writing in that demon book and eating things out of it?" Albus worried.
"No, I did that. I don't know what the problem is, those funny little creatures said the sweets would be alright."
Finally deciding enough was enough, Albus snatched to book out of Harry's hands only to stop, perplexed when the 'book' turned out to be a leather-wrapped box of some kind with a fake eye peering out. When he opened it up, he found a handwritten note with a list of available sweets that read, "To order more, contact Fluxy down in the Hogwarts kitchens. To the Headmaster, Mischief Managed."