The Chaoticlysm. The day that Discord, spirit of Chaos and Disharmony, broke free of his stone prison was considered by most ponies as a day of great fear, confusion, and change. For six young mares it was the beginning of a grand adventure, rich with introspection, personal growth, and a re-forging and strengthening of their bonds of friendship. But, for one special pegasus, life would never be the same again.
That morning, as three young fillies stood arguing about an innocuous seeming statue, Derpy Hooves was happily flying along her route, delivering the News Of The Day to a waking town and reminiscing about the banana–and–daffodil muffin that she had for breakfast. When the fighting of the girls caused the stone of the statute to crack, something happened that drove thoughts of muffins right out of Derpy's effervescent mind. Her thoughts rearranged themselves, focusing more sharply than she could remember them having ever been before.
At that moment, she saw it. A more efficient way to deliver the papers. She sped along, finishing her deliveries in record time. She felt so pleased with herself for thinking of it, she decided to reward herself one of the Cake's delicious goodies.
As Discord took his first breath in centuries, Derpy's mind continued to sharpen, offset eyes constantly scanning and analyzing everything that she saw. When she flew past a strange pink cloud hovering low over the ground, she was immediately aware of its component parts. Or, perhaps that was ingredients. Water, sugar and artificial food coloring composed the cloud, while pouring out was water, lactose, milk fat, and cocoa. She pondered this anomalous apparition for a moment before deciding, with pure logic, that such a thing as a chocolate milk-raining cotton candy cloud simply could not exist. At the thought, the cloud vanished at though it had never been.
She resumed her expedition towards Sugarcube Corner when a strange idea caused her to pause.
"Wouldn't it have been amusing," she thought, "to drag that cloud over to the Ponyville Lake and empty its contents into the water?"
Her eyes widened and she dropped the ground in shock as the realization of what she thought hit her. She shook her head, trying to clear the accompanying image. No, she would never do something so mean and willfully destructive. She couldn't. Could she? Besides, she told herself, that cotton candy cloud wasn't even real. And with that, the cloud that had just started reforming behind her popped back out of existence.
She decided to walk the rest of since since she was already on the ground and would have to land anyway to enter the shop. Along the way, her eyes kept lighting on items that, for the most part, were completely innocent. Her mind, however, started thinking of ways to use them for pranks. They seem harmless; dumping a pail of water on someone's head, high-speed pie to the face, a rolling pin or rake dropped under someone's hooves. She smiled as she walked, allowing herself to indulge in her fantasies.
As the day wore on and true chaos overwhelmed Ponyville, Derpy remained blissfully unaware. Safe in a field of logic, she went about her job building Ponyville's daily mail, completing the task in half her usual time.
Everywhere that her vision encompassed, the pure logic of her mind cause reality to forcibly reassert itself. Soap roads return to dirt, night back into day. One stallion, beset on all sides by buffeting throw pillows, was freed from his torment, only to be re-attacked when Derpy looked away. She was not, after all, stronger than a god. Once her attention shifted, Chaos ruled once again.
She found her mind drifting into pranks, but these weren't the innocent jokes of earlier. She didn't even recoil from the thoughts of holding a pony underwater until the very last second, or dropping a colt into the lake from 30 hoof–widths up. A sly smile spread across her face as the logical part of her calculate the maximum height to keep a drop from being fatal.
A wicked grin split her face as she spotted Ponyville's favorite cerulean speedster, Rainbow Dash, loafing about on a small cloud above the town. A quick mental calculation showed that Dashie would be able to twist around and deploy her wings just in time to keep herself from slamming into the ground. She lifted slowly towards the cloud, careful not to make a sound, watching to make sure that Rainbow Dash didn't look her way. Once she was in range, she gave the cloud a swift kick, smiling as Dash fell with a screech.
Derpy drifted back to the ground as Dash snapped her wings open, catching herself just in the nick of time. She glared at the gray pony.
"Derpy, what the hell? I could have been killed!"
"I just don't know what went wrong." Derpy gave her most clueless smile, her eyes pointing off in opposite directions to reinforce the impression.
"It's fine, no one's hurt. Just be more careful, will you?"
"Sure thing, Rainbow Dash." She laughed to herself as she flew off, not seeing Rainbow go back to a cloud, or seeing her friends come and take her off. She started when she saw a pink earth pony fly by. Earth pony? Fly? She jerked her head around to look, but the other pony was gone. She shook her head, trying to convince her self that she hadn't seen what she thought she'd seen.
Shortly after, Derpy screeched to a halt as a giant rainbow split the sky, separating and covering Ponyville with a transparent pink dome. When it disappeared, she stood frozen, thoughts of mischief vanishing from her head like smoke on a windy day. She found the new-found intellect still intact, immediately recognizing the need to hide the difference from her earlier mindset.