You forgot Cadence
Speaking of Candance, Rarity was able to change Twilight's mane into a porcupine and back into her normal mane, why can't Rarity make Condense's hair into what it needs to be? Does she just not know how to do it, which is why she's using all these tools to try and style it into such? Or is there something i'm missing with pony magic?
On that note, Twilight could have given herself butterfly wings long ago.
If I have to justify an Alicorn twilight in my headcanon, I'll go with the Samothrace Theory of Multilayered Reality.
Basically, there are many "layers", and we can only perceive one layer at a time. However, there are circumstances that allow portions of other layers to seep through, and it's entirely perception-based in such a way that (if done right) it's impossible to tell if you're seeing the same thing that another person is seeing.
