When a Voluntary Shapeshifter's alternate form is mistaken for an actual monster by other humans. For a great example, see the myopic lore behind werewolves: While some werewolves are literally just Voluntary Shapeshifters, others are individuals Cursed (or sometimes infected) with some manner of Involuntary Shapeshifting into a wolf-shaped creature. Thus, it's easy to assume that if you see any character working and living a human life by day, but running through the woods and howling at the moon by night, then you should at least pack a Silver Bullet in case you run into them on a full moon ... right?