After Starlight destroys the time traveling spell, Twilight and Spike get stuck in an alternate timeline where Nightmare Moon is the sole ruler of Equestria.
When Twilight's portals release Tirek into the human world and the humans get turned into ponies, they have to unite with their ponyselves to defeat him and save both world's.
Twilight Sparkle thought friendship was supposed to be about picnics and songs, not fights and hurt feelings. She never sent a report about the reality being a mix of both, but she got close a few times.
There's a new filly in Celestia's school, who finds making friends difficult. She's seated next to a filly who could care less about making friends. Neither is exactly friend material... but sometimes you just have to take a risk...