When Sweetie Belle opens a magical book that contains all the secrets everypony ever had, she's shocked to learn she isn't quite as related to Rarity as she thought.
Forcible reforming can lead to unseen consequences. Like the downfall of chaos and the rise of ultimate harmony. And here you'd think that'd be a good thing...
When Rarity becomes the victim of an invisibility spell, she voluntarily and involuntarily goes through different ways to show herself before Twilight Sparkle can find a counter spell.