xD

Ditto is the redeemed main villain from "the story of Ditto". He is a old alicorn, who many years geleden (same jaar Luna became nightmare moon) was Celestia's most trusted student, same role Twilight 'currently' has. It's obvious that Celestia cared very deeply for him, because she was extremely heartbroken when he blamed Celestia for the death of his family, and she was never able to explain herself.

Due how upset this event made her, Ditto became the one thing that princess Celestia never ever talks about.

However..
Many years later, Ditto runs into Queen Chrysalis after her defeat in Canterlot...