Luna, princess of the night, is in her bedchambers, ready to go to bed for the next night. She lays on her bed, wondering, what if I was the eldest sister? What if Tia was banished to the sun? What if I ruled all?
Celestia, princess of the sun, is at Twilight Sparkle's new castle, helping her set up her new library. She uses her magic to teleport a book, labeled, "Alternate." She opens it to find a spell to switch her sisters' duties. Without thinking, she takes it home, only to see that she is the younger sister.