When your hobby becomes your job!

Parents would find their baby child had been replaced by odd beings who were almost but not quite human.

However strange appearances aside it was their behaviour that marked them out - changelings were said to be either extremely badly behaved - constantly crying and prone to violence, or at the other end of the spectrum strangely docile, often mute and seemingly unable to comprehend anything about the human world they had been left in.

https://www.hypnogoria.com/folklore_changelings.html

Yep, totally a brand new thing that hasn’t appeared throughout human history.

I saw an early screening of that episode at a post-con event at a Star Trek pub in London.

When that scene came on a ripple of ‘FFS - really‽’ laughter went round the room, just because of how blatant it was.

That’s Fergus Wilson - frankly, I’d prefer the leech.