Comment on MLP- The Changeling by EarthnAshes
So when a changeling (let's say female one) breeds with a non-changeling, are their kids always changelings, or is there a chance for them to be the original species?
Depends on who's gene is the strongest in whichever parent. If the changeling parent has more dominant traits, then the child will look more like a changeling. If the other parent has more dominant genes, then the child will look more like that parent. More often than not, if the changeling acts as a dam, then the child will look like a changeling. If the changeling acts as a sire, the child will look like it's mother if the mother is of another species. Other times, though, the child will be very obviously mixed-breed.
What about it's ability to actually change? Does it - at least partially - depend on how many changeling the kid possesses?
Changelings don't actually possess the ability to change themselves in the sense of a shapeshifter. Their magic gives them the ability to produce a physical illusion that mimics whatever living creature they want to mimic, so long as that creature is within the realm of possibility of the changeling. So with that said, if the child inherits that magic trait, then yes, they will gain the ability to "shapeshift", for the lack of a better word. If they don't, then they won't be able to do it.