Swift Quill has been Princess Celestia's personal aide for two years. He takes notes for her, plans her schedule for her, takes letters for her, relays orders for her, and helps everything go smoothly during large scale planned events. Given the nature of his work and its requirement to spend close to every day with the Princess, it’s only natural for Celestia and her aide to become friends.

It is unprecedented that the Princess would fall in love with her aide, however. Of course this isn't a bad thing. Surely any pony would be lucky to have the famous Princess Celestia as a romantic partner, right?

Except Swift Quill isn't a pony.