This artwork is based on the following short story by Kassaz:
https://www.fimfiction.net/story/526921/18/short-stories-with-pregnant-ponies/a-window-of-opportunity

Pinkie Pie worked in Sugarcube Corner’s kitchen, heard Mrs. Cake calling, and left a newly-finished pie on the counter to cool.

Pinkie joyfully returned. “Hello. Did you miss me, sweet thing?”

Fluttershy responded. “Hey, Pinkie. I’m glad to see you too.” Pinkie gasped. Fluttershy was wedged in a not-quite-open-enough window above the pie. “I, um, smelled the pie and, um, um, I’m sorry. Can you help? I’m stuck.”

“Not a problem, girl!” Pinkie hopped outside. The reason for Fluttershy’s less-than-lithe form hung down, pressed against the wall. She tiphooved on a crate. “Dang girl, you sure these ain’t twins?” Pinkie snickered, and couldn’t decide which twins she meant. She grabbed Fluttershy’s tail and yanked. “Wow, you’re stuck good!” She looked for a unicorn. “Hey, Rarity’s dad! Come help me get Fluttershy’s big butt out of here!” Everypony could hear, and see, this.

Fluttershy covered her face with her hooves, uselessly.