Okay now this is officialy beyond weird now,
and moved right now down to freaky town!
First off, I can't really find any major errors in this-partly because it's pretty simple, and partly because I never watched that show before and tried to imitate the style. Her expression is awesome, and I love her natural pose! The colors look accurate and the lines look exactly like the original.
Now for suggestions:
Since this picture is so close to the original style already, I would suggest trying to draw it in your own style, not just the original MLP style. That way, we can see more of your personality and originality shine through, not just the creator/Hasbro's style. Also, maybe try actually putting the pony into an environment where she will have that reaction, like a cartoon strip or animation or something along those lines. Other than that, I really can't find anything that can be improved on without changing the entire picture.
In conclusion, I really like her expression and I hope you learned from my critique!
If you were going for the official My Little Pony (mlp) style, then there's really nothing to improve. The lines are smooth, the colours accurate from what I can tell, the expression tells a story, and the proportions look to be the same as the mlp style.
Seeing as you've done a good job on the pony itself, I'd suggest you try a few things such as:
The pony in a different style from the official one. It could prove to be great fun and will hopefully make you think about how to compose the pony in a different way from the usual. Who knows, maybe it'll make you more aware of any mistakes you're prone to doing.
And if you want an even bigger challenge, try drawing it upside down. It's a great technique for getting out of all those bad habits when drawing.
A background. Now that you've mastered a character on it's own, the next step is to master backgrounds. It'll help you a lot later on if you ever get commissions to have a decent amount of practice with them. Many artists find backgrounds to be their weak spot, who knows, it may be the difference between getting a job and someone else getting it.
Animation! Although this picture tells a thousand words already, it'd be really awesome if you put a little animation into it. The added benefit to animating is you'll have a lot of practice getting your character just right not just once, but many times.