More fae trivia: Changelings are, as the name might suggest, extremely capable of shapeshifting and mimicry, a knack colloquially referred to simply as “changing”.
This ability serves them quite well early in life to better adapt to their environmental conditions, but the ability fades over time as it becomes less imminently-vital. Once you’ve figured out what you need to in order to get by, you seldom have cause to change further, after all. So they pick up the things they need early in life, like the right number of limbs and fingers and such, the right tolerances and sensitivities, the right speech patterns, the right social behaviours to not get them yelled at too much, etc. etc. and gradually their form settles into a more rigid equilibrium.
As a result, most adult changelings can only shapeshift in minor ways, if at all.
An influx of magic can give them a much-needed kick to pull off a reasonably-significant changing however, and a lot of them use this capacity to fine-tune things more to their matured likings.