Mermaids!

Daphnia was a precocious 5 year old with an unbridled love of mermaids.  She watched every show with mermaids - sometimes several times, to the annoyance of her parents.  She was also the child of a powerful sorcerer and sorceress, destined (when she reached puberty, of course) to be a powerful sorceress in her own right.  The problem showed in her fourth year.  Magical events started happening around her.  The experts her worried mother consulted had only heard of this kind of early development a few times in centuries.  Fortunately, they had a solution.  A special suppressor that the child had to wear at all times would keep her from triggering these unwanted events.  The parents had it made into a special crown that, once the child put it on, could not be removed.  

All was well until her fifth year.  Daphnia knew about wands.  Everyone in her parents circle owned one.  They were a focus tool that allowed more precise magic to be performed.  The acquisition of a person's first wand was a significant stage in their life and the community would be present at a special ceremony to mark this occasion.  Children never received wands and, with her early manifestation of magic, her parents decided to take unprecedented care.  When they didn't have their wands with them, the wands were locked in a wall safe.  A wand, in the hands of an untrained youngster, could be dangerous.

What they didn't realise, until the Bureau of Magic investigated later, is that Daphnia had managed to overpower the suppressor.  It had been designed to handle up to double the normal magic energy that a child was supposed to be able to create and focus.  Daphnia was an exceptional child.  It only took 10 months before the suppressor was no longer able to do its job.  One afternoon, just before Halloween, Daphnia discovered that she could "wish" things.  One wish was that she could have a wand just like her mothers.  It appeared before her and dropped to the ground.

"My wand!" she cried exultantly.  It was actually her mother's wand and was immediately noticed.  Her husband quickly cast an ever widening search spell to locate the wand, assuming it had been misplaced.  It took several minutes to located the wand and discover it was in the hands of Daphnia.

Meanwhile, Daphnia was floating down the stream, wand in hand, cheerfully singing a two note, one word song: "Mer-maid".  As she sang the word, she'd point the wand gleefully at some unsuspecting victim.  Man, woman or child, it didn't matter.  Daphnia wanted mermaids and, before the Bureau could stop her, she had many - 28 at the final count.