Twilight needs a date to the Gala after blurting out to a noble that she already had one. The captain of her personal guard, Flash Sentry, volunteers. Things get sappy yet entertaining from there.
In a moment of anger, Twilight says something rash, which is precisely the wrong thing to do with Discord. And now she can't speak, just as one of her most treasured friendships burgeons into something more. She can figure this out.
Ever had one of those days when you wake up to find you've accidentally switched places with your counterpart in a world where you and all your friends are stallions?
Mister Lonely Heart is a self-styled "Grievance Counselor", a changeling who mimics ponies that his clients have issues with. When Twilight Sparkle pays him a visit, he finds out how painfully neurotic the Princess of Friendship really is.