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Tear Jerker: Pattycakes
For me, the saddest, lowest point of the entire ordeal was at the end of Part One. Dash has just been shown a photoalbum of various other "babies" Fluttershy has had over and started to flee the home in disgust. While in the midst of accosting 'Shy for her actions, she messes her diaper as if it were the most natural thing in the world. Dash is shaken to the core by this and breaks down crying. The line that really hits me is: Mommy, I need you to change my diapies. Reading about Dash being so shaken, so broken just leaves an empty pit in my soul.
Compounding on that a little bit. Fluttershy orchestrated this. She intentionally broke her best friend down to the point where she begins sobbing uncontrollably, and all for nothing more than personal gain. The betrayal and shame is put on so thick even the reader can feel it and one feels so sorry for Dash, to the point of tears, themselves.
This scene, which is also featured in the High Octane Nightmare Fuel section of the Pattycakes article, because it can easily be both:
Long story short, after running a gaultlet of tests that Fluttershy subjected her to, Scootaloo is given a choice. She is in one of two rooms divided by a glass window, and across from her in the other room is Dash. Before Scootaloo on her side is a lever. If she pulls towards herself, she gets gassed by the foalmula and permanently regressed. If she pushes towards Dash, then she's one who gets gassed. Well, after reading from a diary which may or may not have been Dash's not to mention recalling a bad anecdote that Scoot and Dash both seem to have forgotten about...for some reason, it's a Troll Fic, it's best not to think about it. The point is Scoots reads the diary, is devestated at what she sees, and...well, just read for yourself.:
"Scootaloo pushed the lever all the way forward. Rainbow Dash’s eyes grew to the size of pie plates as terror gripped her heart. She began to bang on the glass wall, hoping to break it, not realizing it was acrylic glass and therefore could not be broken by her. And the faster she banged on the glass, the faster she breathed in the foalmula gas. She began to cough at first and then felt weak at the knees. She fell back on her padded rear and began to cry. She cried like an infant pony, flailing her hooves in the air. The door to Scootaloo’s side opened and stepped out, leaving the wailing blue pegasus behind her."