It's no secret Princess Luna became jealous and bitter that the ponies didn't appreciate her night but frolicked during the day. All she wanted was someone to appreciate the night that she brought. In order to do that she called upon a long forgotten spell and some very special materials. With a special alloy called equinium she forged a pony that wouldn't have to sleep. When the clockwork creation was completed she added the final touch, the spark that would give him life: a bit of her own magical essence infused into a special crystal.

At first she was happy to have a companion that could enjoy the night she brought. But the joy was short lived. The metal pony never slept so he basked in Celestia's sunlight just as much as he did Luna's moonlight. He wasn't solely hers, no matter how much he insisted she was his true Princess. He also wasn't like the other ponies of Equestria. He had trouble understanding their emotions and interactions, often leaving him shunned and alone.

It was too much for Luna. Not only did the ponies reject her night but they rejected her most labored creation. That bitterness festered and Nightmare Moon arose.

When Celestia banished Nightmare Moon, Luna's magic went with her. And so did the spark that gave the metal pony life. He fell into slumber for the first time but since he wasn't a real pony he didn't even get to dream of his Princess.

A thousand years passed in silence for the pony. Until his Princess returned. With Princess Luna restored by the Elements of Harmony, the reactivated Cloptrap sought her out. She was delighted to see her creation was still functional but knew he would still have the same trouble fitting in as he did before. She kept him with her, thinking that she was the only one that would ever accept him. That was until she herself was assisted by Twilight Sparkle and her friends on Nightmare Night.

At the insistence of Princess Luna Cloptrap was sent to Ponyville so that, with the help of Twilight Sparkle and her friends, he might have a chance to be accepted into pony society.