The Conversion bureau: Heartstrung

In time, humans were alone. Sure they had all the animals to accompany them through life, but they were so different. Humans had no proper way of communicating and there were no real species that had the same intelligence as them. Humans hadn't even made contact with alien lifeforms outside of Earth. Humans were alone, and alone was what they thought was going to be forever.

But one day, an island appears in the middle of an ocean. No one knew how it got there, or what existed there due to a magical barrier that humans couldn't trespass. Little did they know this island was inhabited by multicoloured ponies of 4 races. This was the island of Equestria and the inhabitants happened to be the characters from the exact same show by Hasbro. Coincidence? No one knows.

Shortly after the islands appearance, the ponies made contact with mankind. Things weren't good at first but they learnt to live with each other and cooperate with their lives.

They than started up a chain of conversion bureaus where humans could be ponified if they wanted. This gave a new opinion to the human race and the sentient beings that would be loss from lack of worth.

But there was one pony that didn't seem worthy as a pony. She thought that life as a pony was worthless and boring and thought that humans were more interesting. This was Lyra Heartstrings.

Both species have been so in depth with ponification they didn't even know if Humanification was possible and didn't sit anywhere within that area. It was Equestrias pony magic that made ponification possible so humanification may not be possible.

But there's a chance there's some magic or science that could make it possible.