Vision- Story that you made is like movie scenario for me. It has everthing- Opening (Little naive, but in positive way) development, and ending with perspective for more. clever characters, explanation of some motives (For mlp fans things like Lyra human addiction is obvious, but not for random readers).
Originality- I don't see anything wrong, that Doctor, or almost any of characters are not your idea in 100%. Thanks to that they are closer to us, and your ideas like Iron Will backstory, bringing them even closer.
Technique- from the beginnig to the end, a classic mlp line- I don't see any different, and I love it. Also a distribution of frames (I don't know proffesional designation) is very good.
Impact- Ussualy I avoid writting critics, even if something is great, but here I spend a really good time reading this. I'm sure that your story will stuck in my head for some time <img src="
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I'm very sorry if I did mistakes that makes this critic unreadable- English isn't motherlanguage for me :/