Cool animated tentacles!

Creepy as hell : D

You pulled off those pesky protuberances perfectly. And I don't think he should be breathing. It is not in his nature to breathe. Maybe some other kind of subpixel animation could be used around his frame, like the flickering from this: www.pixeljoint.com/pixelart/49971.htm

This animation is simply fantastic!

 The tenticals look amazing, difficult to animate well in my experience. The only thing I would say is that it would be great to add a breathing motion to the animation. Just a slow bob up and down of the head and shoulders.

I re-uploaded it in the original size. Background is Operator symbol which is related to Slender man.

The animation is very good, but in my opinion it would look better if it was not upscaled and if it had a faster framerate.

Also I don't understand the background, and it looks messy on a bright background.