Well Discord if we involve him as a kid I'm thinking he could be the one who had first caused Parasprites to exist as he want to make something for possible friends as unlike most other beings Luna Celestia and Chrysalis was nice to him and didn't act like he was strange or freakish but do to his chaos magic when he made the three little creatures even though they was cute ,nice and fairly harmless the things had that eat everything then make more of themselves by puking thing going on even though Discord hadn't had the last 2 things in the plan when he made them. I'm thinking he got the ideal to make the parasprites after seeing this transpire
http://flausch-katzerl.deviantart.co...ssey-262136613
Luna and Celestia get in a fight over something Luna runs off gets lost in the Everfree forest finding herself at the edge of it ,getting extremely scared cause of it but do to Discord having came across the filly had made several clouds pink that started to snow which soon changed to cotton Candy and Luna had a good time from it.
Chrysalis who had planned to play a prank went to transform into Luna ending up with this
As a result
and perhaps sometime we have something happen after a timeskip or something that leads to this
http://flausch-katzerl.deviantart.co...ting-264986244