AN: From interactive "Transfiguration", chapter originally written by Mr. George.
Harry wanted to impress Professor McGonagall with his transfiguration spells. An ability to conjure a disguise would be invaluable for someone hoping to be an Auror.
After careful (well some) research, Harry found that keeping to human form was the simplest, with a complete animagus form being the most difficult. Some were relatively simple, and while he had enjoyed Tonks' games with changing her nose, he doubted it would impress his Head of House.
Swallowing nervously, as the idea built he knew what he needed to do. A gender transformation was key. All he had to do was prove to the professor that it wasn't merely polyjuice. The girls bathroom was as quiet as ever, with only Moaning Myrtle occupying it. It's reputation wasn't helped after the discovery of the entrance to the Chamber of Secrets. Besides, there was an amusing irony or parallel with surrendering his masculinity in this room.
Facing himself in the mirror, he tried to imagine the changes. It was essential for the final swish of the wand, and would help him concentrate on his female form as it developed. He... She could guide it, so that..
A frisson of excitement raced down his spine. Did he want to be a cute girl... or mousy and anonymous... The idea of being abundantly feminine made him smile then blush.
Snarling at his reflection, he screwed his courage up.
Without further delay, he started the spell. Until at the climax he shot a beam of diamond sparks at his reflection. The bathroom vanished in a blinding flash. Even blinking, and eyes watering Harry could feel the spell working.
It wasn't going quite as Harry expected. Harry felt his uniform begin to slough off. Spreading thin in places, the merest brush of his fingers causing it to turn to dust and drift to the ground. Rubbing his watery eyes, Harry still couldn't properly make out his reflection. Leaning forward he peered deep into the mirror, his face just inches from the glass.
Only when he removed his glasses did everything jump into focus. He saw the reflection of Myrtle, attracted by the flash of magic she watched. Her hands folded atop the cubicle wall, her gaze fixed on Harry's cute rear end. Catching his eyes, she giggled, and gave an approving nod.
A tingling from his chest brought Harry back to think about his imminent changes. Already he could see his nips spreading wider, and rising higher. Instinctively, his hands rose to confirm what his eyes told him. A gasp escaped his lips, as his fingers brushed over the new nipples. This drew another giggle from Myrtle. Harry's stomach twitched painfully, and he felt his waist pinch inwards. He'd never been fat as a child, but now he... (a glance downwards confirmed this)... he was getting some significant curves. A crack announced the shifting of Harry's hips, as they widened, adding the curves.
There was a disapproving pout on Myrtle's face, as Harry's arse started to swell. Growing from a taut male posterior, into a fulsome and rounded rear. Running his hand over the developing ass, Harry spotted that his fingers were slender and feminine, and tipped with a glossy nail varnish.
Dismissing Myrtle, Harry tried to concentrate. He needed to concentrate if he wanted to have any hope in directing his transformation. Pressing forward against the edge of the sink, Harry found that she was now the right gender for the toilets.
