I use blender, although it's not the easiest tool to start with, but it is really powerful and also free! There is something called masking, which makes it kinda easy, but still a lot of manual work. That was honestly the part that took the most time. Also that's why many of the faces have some ugly edges. I probably should have spent more time on this, but you know, one also has to live. ;)
Here is a video tutorial that show essentially the method I used, except that I used an Alpha Overlay instead of Blur: 21 - Blender Video Editing(Face Blurring / Masking with UV-Image Editor / Auto-Keyframe)
I could make a short tutorial on how I did a scene with all the heads and stuff, if anyone is interested.
And so spawns the new generation of meme-producing FReepers... they’ll take the world by storm haha!