Not exactly how you put it, but yes, you got the idea right. I had only the black color copied from a few screenshots and stacked the copies all over. Learned this trick back in 2007 on that old static game. Doesn't work with moving objects though, but "impossible to screenshot" is quite an exagerration at this point. A moving background would make it harder to pull off, but with it being merely "static" statics there's even more - inverting colors in a half of shots and stacking the white only can effectively de-noise the background, leaving only the noisy objects.
Making a few copies like this and extracting the black color again to stack it all over the place will make these objects more opaque, but with a clean background this time. I suddenly felt apathetic so I shaln't bother with making the further example, may I?