Why did the changeling army choose to invade Canterlot during Princess Cadence and Shining Armor’s wedding? The answer can be found in a chance meeting between Queen Chrysalis and Nightmare Moon, back at the Summer Sun Celebration …
Something has gone wrong with the Crystal Mirror and it just so happens to be on a day when Princess Twilight is rolling out the red carpet for Princess Ember. Could Twilight have made a mistake when she rigged up Celestia’s book to the portal?
Why didn’t Princess Luna come to help fight off the Changeling invasion during Shining Armor’s wedding to Princess Cadence? Now we know - she was having a few problems of her own in an alternate universe where Nightmare Moon ruled unchallenged!