The alien was made in Makehuman / Blender. The fog was rendered in Blender (smoke) but I rendered it apart from alien and walk tinted and bluescreened in Kdenlive. Greyscale fog does not work. Anyway lightly blue / green fog was better for this scene. Also the background was bluescreened in Kdenlive to save rendering time in Blender (The camera was fixed and not moving).

http://youtu.be/bUZgwPW5tcc

Damn that looks creepy, I think if you would of used more contrast, it would look creepier, luv blender, also nice compositing