A nameless human finds himself waking up as a pony in his sleep, believing it to be a dream until Princess Celestia comes along and tells him his purpose. Celestia had grown a bit tired of the letters from the Mane 6, and used a spell to bring someone from another world, to get a different perspective on friendship in Equestria. The pony is more than happy to agree and sets off for Ponyville to make new friends and go on adventures while learning about friendship and whimsy, or at least trying to.
(yes this is a shameless self insert now shut up)