Okay, so here's my first attempt at making a creepypasta. Enjoy! :)
"That's weird," thought Twilight Sparkle as she took a bite from the cupcake Pinkie Pie sent her.
"This cupcake tastes entirely different from the other cupcakes Pinkie makes! Maybe she added a new ingredi-"
Her thought was interrupted by a loud whirring noise and a pain so excruciating it was impossible to describe. Twilight's eye bulged. She took the cupcake out of her mouth, rushed to the washroom, opened her mouth, and looked at the mirror. She screamed. Her mouth was full of nothing but blood. She couldn't see her teeth or gum, just blood, blood everywhere. She screamed even harder, and some of the blood trickled out of her mouth and fell into the sink.
"Enjoying your cupcake?" A strange yet familiar voice said. Twilight turned around to see Pinkie with a smile like a knife. And speaking of knives, she had one in her right hand. The other hand held something blue and familiar. Twilight took a closer look. It was the dead body of Rainbow Dash! As she looked on in horror, Pinkie laughed and begun to put her knife to use.
As blood trickled down her giant gap in her neck and made a puddle on the floor, Twilight tried to gallop away from Pinkie. Pinkie laughed again.
"Oh, come on!" she cackled, "already leaving? We haven't even begun!" Pinkie caught Twilight by one of her front legs, and carved some pictures of rainbows and happy faces and cupcakes and stuff like that on Twilight's stomach. And Twilight screamed really loud and stuff.
AND THAT'S THE END.