I have a question!
What would happen if Fluttershy use to have two personalities? One that takes care of animals and is nice to everypony, and another one that tortures animals and is mean to everypony, even royalty.
What if years ago, when Fluttershy was a filly, the kind Fluttershy and all of Cloudsdale got rid of the cruel personality and was rid of it ever since?
Finally, when a legendary event, the Blue Harvest Moon, happens which has an effect on every animal in Equestria, what will happen when Fluttershy's cruel personality comes back once again?

I got the idea from the show Total Drama All Stars.

What can Fluttershy do when she has a problem? Not just any problem. A problem that may change how everypony sees her. A dilemma that can make her look like a threat. A terror. A freak. A monster. Who can she turn to for comfort, without having them fear her? At least she's still Fluttershy... right?

Rated Teen for a scene featuring violence and blood. Tagged 'Alternate Universe' because I don't believe her change to be permanent, but I still thought it would make a good story.

Fruit bats don’t drink blood. However, when Twilight reversed the spell that turned Fluttershy’s usually timid nature into that of a vampire fruit bat, the transformation was already complete. The reversal caused Fluttershy to lose interest in the apples the fruit bats craved. Now, instead of sucking apples dry, she craves the blood of live ponies.