Everypony knows of the reign of chaos a thousand years previously, when Discord ruled all the land with no mercy, but not one of them has ever questioned how he came to be . . .
You have been in Equestria for sometime now, and even though most hate you, you find peace with the princess. Until Celestia proposes something you must refuse.
Another ancient villain of old appears in Equestria after his 1000 year imprisonment and Twilight is angry because of it! Not at the bad guy, but at Celestia for failing to mentioning ANOTHER powerful, sealed away villain that managed to escape.
SPOILERS for Gravity Falls' season 2 & finale + MLP:FiM season 6: "The Crystalling". One year after Weirdmageddon, the Pines reunite in Gravity Falls for another summer of adventure. A fall into Equestria as ponies wasn't what they had in mind.
Fluttershy has broken through to Discord, but there's still a lot of work to do. Between "Well played, Fluttershy" and "Friendship is magic!" there was a whole new story.