On the Winter Solstice, Starlight and Twilight's definitely-not-a-date is interrupted by Sunset Shimmer arriving from the future. Warning of a disaster, and claiming to be Twilight's future wife.
A mixup at the mirror pool separates Pinkie Pie from her alter ego, who then has to learn how to live in a world where she can't count on Pinkie's cheeriness to take over again.
“You are hereby invited to the wedding of her royal majesty Princess Celestia of Equestria.” Twilight is stunned when she receives this message, especialy since she didn't know that Princess Celestia had been seeing anypony...
Morning Glisten isn't really a good filly. She fights with other foals, and she doesn't really trust adults. So when three Princesses take an interest in adopting her, she'll need to become someone else to win their love.