Since seitora's rezzed this thread, I thought I'd add something I've been thinking up the past couple weeks.
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It was the morning of the First Task, and Harry Potter had just stepped into the Great Hall. Immediately, every eye was upon him, likely drawn to the sudden, massive change to his physique since the previous day. Gone was the short, scrawny teenager who moved as if the entire Wizarding World was atop his shoulders; what stood in the doorway was a tall, muscular looking young man who moved with confidence and purpose. Striding briskly towards his oldest friends, he sat down opposite from them and began to pile his plate with enough food to draw stunned looks from the Gryffindor students in his immediate vicinity. All this was not lost to Hermione, who chose that moment to state the obvious.
"You look different, Harry."
"I have no idea what you mean," Harry innocently replied, as he began to consume his gargantuan breakfast; the act of which had Ron staring at the amount of food on his plate.
"You look like you've gained a foot in height, probably 100 lbs of solid muscle, and you're eating enough food to make Ron jealous." the bushy brunette stated, gesturing to their mutual friend, who unsubtly wiped the drool from his chin as he looked upon the food.
"Maybe I finally hit puberty and had a growth spurt?" the Looping wizard commented between mouthfuls. The only reply he got was a condescending eyebrow raise. "Anyway, the First Task starts soon, and I'd like to finish my breakfast and get ready before it does; so we'll talk about it later, promise."
"You better" was all the bookworm said, before returning to her much more modest amount of food.
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Time passed, and it was almost time for Harry to go up against the Horntail in the First Task. Events in the tent earlier had been rather amusing for Harry, mostly from the reactions of the other Champions and Ludo Bagman to how he now looked. There was the dumbstruck looks from Krum and Diggory, the barely contained glee from Bagman, and the way Fleur acted around him, clearly aroused by his new physique but doing her best to pretend she wasn't. After the four Champions drew out their respective dragon models representing what they would be going up against, and in what order, Harry settled into a meditative position. That said position was floating about 2 feet of the ground did nothing to reduce the shocked looks of his competitors.
Harry snapped out of his meditation the moment his name was announced outside of the tent. Dropping back onto the floor, he stretched out his muscles, focusing on the ones in his shoulders and neck, and stepped forward into the sunlight. Looking up and around, he could see the amassed crowd of all three schools with the Hungarian Horntail in the centre of the arena, perched above a clutch of dragon eggs. Breathing in deeply, he knew it was time to start the show. Standing with his legs shoulder width apart, his arms tucked close to his chest with his hands balled up into fists, Harry concentrated on his energy, and began to draw it out.
It began subtly, with only those who could feel it noticing it happen, but quickly it became apparent to everyone there, even if they didn't know what it was. The first obvious visual clue that something big was happening was the ground around Harry's feet began to break apart, seemingly being pushed by an invisible force. It was then that Harry began to yell out in earnest, rather than the muted grunting he had started with. As his scream increased in volume, so too did the waves of energy, eventually causing the entire arena to shake from the force of impact. When his voice reached it's peak, a blinding light erupted from his body, temporarily blinding everyone with it's intensity. When the light faded, and everyone could see again, they were greeted with the sight of Harry Potter, still standing in the exact same spot as he was when this all started; but now his musculature looked even more intense than it did that morning, along with bright blond hair sticking up in spikes, green-blue eyes, and a glowing yellow aura surrounding him. An instant later, he launched himself at the dragon, eager to see how it would fare against him.