Twilight might be required to take on the Spirit of Chaos - in all that that entails - to fully ensure that Discord's place remains with the friends he has made, and with her.

Interesting alternate or deleted scenes from my Sympathy Series

Discord’s lack of empathy and a pony's sensibility has been tolerated by Celestia, but while both the princesses and the bearers of the Elements of Harmony struggle with even more dire problems, Discord is forced into a lesson of his own.

Once there was a pony who could bring the dead back to life, who solved murders with a Griffon PI. Their investigations lead them to Ponyville & to team up with Pinkie Pie [Pushing Daisies crossover]

A conversation with Discord causes Twilight to question the particulars of true harmony.

With the Doctor's help, Shining Armor finds Twilight again, only to find she doesn't know him.