Fluttershy wants nothing more than to make Macintosh happy. She tries her best, but no matter how hard she tries, she can't please him sexually.
One tear-filled confession of her problems to Pinkie Pie later, and Fluttershy finds herself roped into throwing a rainbow party for Big Mac with her friends. If you know what a rainbow party is, you can guess what happens next.

The characters in this story are anthro, but they fall more towards the human side of the spectrum. Basically they're fully humanoid with colorful skin, pony ears, wings/horns when applicable, tails, and cutie marks on their lower back or someplace like that.
WARNING FOR BORING PEOPLE: Chapter four contains a healthy amount of wincest.

Original idea proposed by Bronystories and nicked by me.
Cover art by the wonderful french-teapot with text slapped on top by me.