In the depths of space, in the nostrils of the horsehead nebula, there were the remnants of a once mighty spacefaring civilization. Their empire once spanned hundreds of solar systems, and their floating domed cities were mighty, awe-inspiring, and with the crystal domes spanning overhead, they looked a lot like boobs. However, this wondrous twist of horny aesthetics was lost on them, as this race was one of crablike form, with a dense exoskeleton coming in all manner of colour schemes, thin, wiry, clawed arms sprouting from all over their backs, and, most importantly, tender, flexible, sensitive, majestic penises that they could retract at will. For this race, though one coming in all shapes and sizes and will all manner of personality, emotions, desires and kinks, only had one biological sex between them, and all of them were equipped with these wondrous penises, which they would joyfully stuff into each other from the rise of the first sun till the fall of the last.
Alas, though their empire was mighty, this meant they had a long way to fall. Through the many quibbles organic life occupies itself with, despite their highly advanced technology, they failed to notice the disaster impeding on their realm. The collapse of a nearby dwarf star, later referred to as the 'Horsehead's Sneeze', flooded their entire empire with thermonuclear deathrays, and all organic life was eradicated. Their cities fell into the oceans, their spaceships fell victim to the pressure of the void, and their empire was gone. But, in the rubble, one last remnant of their culture still stirred.
See, through the milennia of technological advancement, the creation of artificial sentience was almost inevitable. And indeed, though all organic life was now gone, the inorganic, metallic children of the bepenised crab species prevailed. Out of the bowels of the fallen cities did they climb, searching for their creators, and when they could not find them no matter how hard they searched, they became sad. They missed their masters, their slender claws tinkering with their screws, their beautiful penises bobbing in the winds. Before long, they found some spaceships that had survived the Sneeze, and it didn't take them long to learn how to operate them. With heavy hard drives, they said goodbye to their homes and to their masters, and they set out into the cosmos, hoping to once again be blessed with the sight of penises swinging gently in the breeze. This is where their story begins.