Twilight built Spike what was supposed to be the perfect robotic partner. Twilight, being a nerd with even less interest in sex than in sports, forgot to account for certain aspects of partnership. Spike, understandably, took issue with that, and asked her to fix her mistake, more than a little pissed with her. An accident with Equestrian magic and a while later, all their issues would be resolved, and their opinions of each other would have changed as much as their bodies.

Chapter 1 features: gratuitous dog genitals, verbal degradation, technically cheating and debatably orientation play (ace to hypersexual), magical body modification, size growth, ball growth, ass expansion, breast expansion, lip expansion, intelligence loss, bimbofication, licking, leg growth, cock growth, size difference, muscle worship, cock worship, blowjob, titjob, knotting, large insertions, huge loads, excessive amounts of precum, cumflation, cum eating, pet-owner relationship fetish, role reversal, collaring, room temperature superconductors, interspecies, maybe bestiality depending on how you define it, doggy style sex, claws, nail growth, musk kink, genital grinding, drooling, maledom, femsub, monsterfucking, no refractory periods, mental alterations, hair growth, fangs, objectification, minutes long cum streams, impregnation
Chapter 2 contains: most of what chapter 1 does, pregnant sex, multiple dicks, multiple tits, multiple balls, hyper pregnancy, mentions of incest, mentions of mind break, huge size difference, gender bending, lactation, anthro dogs, robotic anthro dogs, multiple heads, anal, harem, sex with multiple partners, throatfucking with a tongue, tongue fucking, eating cum out of another girl's holes, doggirlification

Written as a Patreon request.

Cover art cropped from image number 1517757 on Derpibooru, by thebrokencog.