So close!
The writing was for the most part excellent, very funny at times and some great subtle jokes (like Derpy's nature being up for debate another time).
However the direction (both in performance and camera) did get a little tedious; would have been a 4 1/2 out of 5 in my books if only it was a little bit more mixed up- having them walking and talking to make the scenery pass and be more interesting, or attempting a shot from any angle besides side-on would both have been great ways to make the scenes more visually interesting at no cost to the character's performances.
Fantastic job emulating the FiM animation style, especially facially! But as I said the static poses became a little tedious (There is a LOT more movement in the series). The voices were good, Derpy's being an absolute triumph, however The Doctor's voice felt far too put-on.
Not only did the pronunciation sound too carefully considered, but those simply-not-true British sounding phrases came straight from a stereotypical comedic Dickensian character, and not the naturally charming British vocabulary that many of The Doctors have possessed. With a natural sounding Doctor voice that aforementioned 4 1/2 star consideration would be a 5 all the way!
Looking forward to seeing yet more from you, and please consider varying the pace and camera direction in the future, I believe that would stop all these pony haters neigh-saying and calling it 'easy', 'simple' or 'lazy', because to say that about such a great attempt at the TV-quality style is just wrong!