Kinda neat. With minimal animation and only three or so backgrounds you managed to make an entertaining flash. Moreover, you managed to make an entertaining MLP flash that didn't have Spike.
Here's what I liked about it:
-The art was solid. Very clean and precise.
-The animations were good. Nothing too complicated, but decent for what was there.
-The audio was good. There was a difference in audio quality between the two voices which was mildly distracting, but by themselves each was decent.
-The idea is... Unique.
Here's what I didn't:
-I don't get how he was magically changed into a horse. I realize that it was the only way to keep the bit with the... Pen thingy that I can't remember the name for in there, but other than being a plot device I don't see how it made any sense.
-Spike is nowhere to be seen.
-The flash worked for a conversation and could have ended with him leaving, but I don't feel like it really set anything up for the next part. I just don't have that "I wonder what happens next!" feeling. Some subtle foreshadowing would be nice to keep viewers intrigued.
-Spike should be here but he isn't.
-Although the animation was fair for a "talking heads" situation, they really didn't move as much as they could have and they didn't interact with the environment at all, which caused sort of a boring disconnect between the characters and the background.
-There's a character named "Spike" who is the only good thing to ever come out of My Little Pony. You should have found a way to incorporate him.
Overall, this is a good flash with nice art and enjoyable writing, but more could have been done to set up what appears to be an inevitable sequel.