CT-0962 "Impact" was an ARC trooper sniper who was killed during the Massacre of Devaron. When he was killed he was transported to the World of MLP. After spending a few months in Equestria, with only a few ponies knowing of his existence; he exiled himself deep in the eastern part of Equestria. Soon, recent events will lead him to coming out of exile and rejoining society.

(I don't own MLP or Star Wars)
Also, a worthy note is that if you know about the Massacre of Devaron than you will know that there weren't any ARC troopers there. But for this story, we are just going to say that he was there.