I'm always a fan of good crossovers and NG + MLP is certainly an interesting one at that! The first thing that caught my eyes, aside from the majestic presence of Fluttershy was the wild colors you used to fill the background. While we're on colors, I see the brilliance in your arrangement; Pico's "shadow" is a bold fiery red that reflects his hot-headed and famously violent nature. On the other hand we have the gentle Fluttershy who's foundation is an elegant and shimmering puddle of indigo. But what's to be said of the darkened grass behind her? Hehehe... it's a good thing she'll never run out of love from her fans! Facial expressions are dead on, not to mention Fluttershy's excessive politeness :3
However, the *SMACK* cue seems unnecessary to me since you have lines to indicate the hand's movement directed towards the face, thus being redundant. It's a slight thing but all in all I'm still lovin this. Great work!