Rainbow has always wanted to be a griffon. Twilight agrees under the condition that Rainbow finds her a griffon template, and thinks that's the end of it since Dash won't be able to. Except that Dash ends up convincing Gilda, under the condition that Twilight gives Rainbow a dick while she's a griffon. Impregnation, science, and then more impregnation ensue. Oh, and Spike's in the story too (but doesn't get some til chapter 2).
Story is marked complete, but depending on how popular it is I may make more chapters later.

Alternate ending to "It Ain't Easy Being Breezies", obviously.
Cover art is #725751 on Derpibooru (mature and unlike this story is a fully female griffon Dash)

A dark version of this has been written and is available here. It doesn't differentiate until the end of the first chapter after Rainbow impregnates Gilda.

Basic Contents: futa, sex (anal/vaginal/oral/hornjob), magic, impregnation, transformation, scalding hot dragon sperm

Detailed Contents

It's a Chapter 1

It’s a Breeze: bad ideas, implied vore, griffon bitchiness

It’s a Spell: attempted public sex, fondling, futa, heat, imminent breeding, magic, transformation (species/gender)

It’s a Test Drive: aggressive submission, blackmail attempts, cunnilingus, dangerous blow job, deep-throat, foalcon (barely), futa on female, heat, imminent science, impregnation, public sex, rocking the tree house, sixty-nine, vaginal, voyeur

It's a Chapter 2 (Will be published sometime next week)

It’s a Science: bisexual, choking (light), cunnilingus, lesbian, excessive (mare)cum, futa on female, gargling pussy juice, hate sex, hornjob, imminent foursome, impregnation, predators with prey, squirting, threesome, vaginal

It's a Foursome: anal, bisexual, boiling dragon cum, cunnilingus, double penetration, double-pregnancy, female on female/male, futa on female, hoof fetish, hornjob, horngasm, lesbian, magic, purring, straight, unconscious sex, vaginal