“Like I said in this picture ( >>513510 ), I normally draw young changeling queens with young Fluttershy’s body type, so I wanted to do just that. And since I didn’t draw Myxine in that pic, she’s the perfect fit.  
So this is an actual “canon” pic of Myxine shortly after she’s born.  
Now she has to go out into the world and make her first husk to prove herself worthy of being queen.  
Normally young queens instinctively assume the shape of a foal because they know it will get them the most love. Sometimes they simply turn up at the doorstep of a childless couple, but occasionally, after keen observation and thorough analysis of the risks, a queen might replace an existing child to gather even more love. This is where a common misconception about changelings comes from, that they replace children in the cradle - when in fact it is only queens that can do so.”