The Nightmare Initiative is a Fallout: Equestria side story. It currently has 5 chapters totalling 26,312 words.
It can be read on FimFiction here.
Fallout: Equestria- The Nightmare Initiative follows Bright Idea, a pre-war scientist, as he travels the length of the Crystal Empire and beyond in an attempt to figure out why he's alive.
Bright Idea spent the last two-hundred years in a cryogenic sleep, complete with a simulation that created a perfect life for him. The war had ended, he had a loving family, and Equestria was beginning to rebuild. One fateful day, his life is turned upside-down as his wife tells him to make his way to Sugarcube Corner moments before he is thrust into an unfamiliar world.
Bright wakes up in Stable 117 with one clear goal: get to Sugarcube Corner and figure out what is going on.
The Nightmare Initiative takes place in the Crystal Empire, with Bright Idea waking up roughly two-hundred years after the Great War.