6) Alien/Aliens
A more obvious reference point for the Upside Down creature/demagorgon than The Thing‘s monsters is clearly the xenomorph. Specifically, the Duffers appear to be drawing from James Cameron’s Aliens and Ridley Scott’s original Alien.
There’s only one creature, as in Alien, but as in Aliens we go behind the scenes to see how the creature sets up camp, making itself a slimy nest and ‘storing’ people in cocoons for later use (namely eating them and, as is hinted at the end of Stranger Things season one, implanting in them some living thing).
There are visual callbacks to Aliens, too: the creature is shown to be almost impervious to bullets, but screams in agony when touched by fire. The two creatures even look similar: The demagorgon is, like the xenomorph, a nightmarish humanoid that stalks its prey from the shadows, clambering along ceilings and walls and often appearing out of nowhere.