Pinkie Pie gets sad sometimes. It's just a fact of life, and it's one Fluttershy had to get used to when they got together. Sometimes Pinkie gets sad, and all Fluttershy can do is be there for her.
Pinkie is brash during these episodes, though, and that can cause problems. Such is the case when she's spending time alone at her "thinking spot," the mirror pool in the Everfree Forest, and an accident leads to her falling straight into it.
The magic of the pool splits her in two, and suddenly there's a new Pinkie in town. She isn't there to party, though, and her sour expression and flat mane don't seem like they're going to disappear anytime soon.
She'll just have to learn to live with it.
This story is set in the same universe as most of my other stories, and as such the setting and characters may be a little different than they appear in the show. None of my other stories are required reading for this one, but they do have context for why characters may look slightly different or live in a different town.
Going the other way, this story does have slight spoilers for other stories in the chronology, notably for my last story.
If you'd like to read the other works in this universe, you can do so here!