He begins to use them to cause the residents Butterfly Valley and Troll Kingdom to become undead fly-like beings who are loyal to him.
King Boogieman, however, kills the Fly King by turning him to stone and cutting off his head. Princess Butterfly's powers are then returned to her, and she returns the kingdom to normal.
- The Fly King may be a reference to Bezelbub, a name for the devil meaning "Lord of the Flies."
- It also may be a reference to the book Lord of the Flies since The Fly King has a pig-like appearance, and his minions appear to be children wearing face paint.
- Many consider this a canonical error, as it's stated by Frank that one can only gain her powers through marriage.