Well, apparently the animators in the new episode thought they could sneak something under our noses. Which is funny, because some people have been searching for Derpy in the background since Season 3.
You might as well call it Pinkie Apple Maymay, because this episode was filled with them. First was Applicious, then DustyKatt (Dusty Cat, clever) and now this. If you didn't quite see it in the first picture, maybe this gif will shed some light.
Yes, what appears to be the infamous Slenderman made an appearance in this week's episode. Now, if the animators are as based as we think they are, they probably would have colored this guy green, giving homage to Anon in Equestria, a popular general on /mlp/. Now, we're not entirely sure that this is our no faced friend, but we're not sure what else "it" would be.
What will Season 4 bring to the table next?
What general will make its appearance in Episode 10?
We can only wait patiently for the new episodes to find out. (That is unless some anons get to bruteforcing, but that's another story)