Actual, physical special effects are always welcome, and seeing the Demogorgon's head as an actual animatronic is great. But there's something about this jerky test footage — maybe it's that the head isn't attached to anything — that makes it almost creepier than in the show.
Spectrial Motion, the makeup and animatronics house behind the monster, posted this test video on its Facebook page:
The video gives a look at the animatronics test, but Spectral Motion also posted photos showing how the full body was created. And, again, there's something very weird about seeing it broken down into steps like this.
I think it's the bright green shoes of the man inside that really sells the weirdness.