It came to Twilight suddenly one day. The day Applejack broke a Pinkie Promise. Twilight remembered being in a changing room, trying to coax Fluttershy and Rarity into telling each other their secrets. But something was different. She did spill the secrets: Rarity actually hated Fluttershy’s fame, and Fluttershy actually hated being famous. As her friends made up, Twilight realised that she wasn’t trying to shove her own hooves - or fruit, or a potted plant - into her mouth. Quite the contrary. Something was pulling itself out of her mouth, literally. Something pink, with a poofy pink mane, and blue eyes narrowed in sharp disapproval. As Twilight gagged on the pink pony who had somehow pulled her head out of Twilight’s throat, the eyes then narrowed in a different way, elongating out of her head, tapering into blades. Her mouth fell open, her upper jaw receding into her face, her tongue elongating and lengthening into a blade itself, sharp and deadly. The Pinkie’s eyes and tongue converged on Twilight’s horn, as though to pluck it off…  
Did Twilight still have a horn? She knew not for sure. It was a secret The Pinkie kept well. All the magic Twilight had thought she’d been casting may well have been cast by The Pinkie, to keep the secret of The Pinkie. For “The Pinkie” she was. “She” was no “she”, nor was “it” even appropriate. Pinkie Pie was Pinkie Pie, singular and incomprehensible in every sense of the word. If Twilight’s horn was gone, it was a trick that even fooled Discord, who would have attempted to remove something that was no longer there.  
It didn’t matter, though, because Twilight now lays shuddering on a padded floor, imagining further tales of the magic of friendship, rubbing her forelock against the padded wall, trying vainly to convince herself that her horn rubbed the wall as well.  
Now she knew why Pinkie Pie so valued keeping secrets. It was not only good when friends could all get along, and keeping secrets meant keeping the peace.  
No.  
The reason that thing, that incomprehensible eldritch being placed such stock in withholding certain truths:  
There were some secrets that were better left unrevealed.  
FOREVER.

HHerobrine

TS: Fluttershy, you new painting is horrifying. I’m glad I know this unseeing spell.