The little creatures themselves / what about them scares us / remake possible (Possible spoilers in that I paused the VCR in 1984 and photographed the creatures. Let's face it, you the reader's not knowing what they looked like made the movie scarier)
Rather than summarize the movie (as other posters have done), I would like to comment on the primal fear in which movies like this evoke. I would also like to offer some suggestions for a remake.
I first saw this movie when I was eight or nine years old, in 1973, first on a bad, wavy black-and-white T.V. and later on a sharper color t.v. that same year. About 10 years later, in 1984, someone taped the movie and I borrowed it, pausing the VCR to photograph (with a 35mm camera) the creatures themselves in the instantaneous frame or two when the creatures were actually visible.
There really wasn't much to see. Their bodies were dark, probably furry and anthropoid, their faces/heads were bald, shriveled and ghoulish, their eyes dark as if covered with glasses (giving possibly a skull- or possibly alien- effect), and they had small hands with claws. Like mice, they were impossible to corner, you could only see parts of them as they departed into unknown exits/gateways. They definitely had some physical limitations because of their size but were extremely efficient at improvising and overcoming these obstacles. They could have been anywhere from 12 to 20 inches in height, I tend to favor saying 16-18.
They feared the light, which we presumed anything brighter than a candle or two was extremely painful or lethal, like a wall of fire.
It was this undeniable sense of mystery and fear of the unknown that made this movie so creepy: Being watched -- merely that, is shocking enough. Then, the foul, threatening-yet-beckoning whispers in the dark, echoing weirdly and sharply in a big, dark old house; the fear of having some unseen presence tug on your clothing but only getting a glimpse of what the thing was before it glides off into the corner or around a piece of furniture, the fear of being abducted and taken to foul, netherworldly dimensions, and the fear of transformation itself: being changed from a normal human who thrives in daylight and open freedom into something unspeakably foul, grotesque and sub-human, and confined to darkness even when 'freed'.
Even though the creatures seemed quite physical, they had a certain ghostly quality about them, and the ability to appear and disappear and get through places where there was no opening or route of escape. I tend to side with the posters who do NOT think of these creatures as 'demons' -- but something else. (Demons are too broad a category). Thank God so much was left to the imagination. I tend to think of these creatures as a nasty, vile, sub-anthropoid species perhaps like trolls, goblins, or some type of primitive hominid which, nonetheless, had vast inter-dimensional gate/teleportation abilities. Something perhaps banished from the earth or imprisoned long ago, accidentally released and reimprisoned, released again, and desiring to replenish or repopulate.
A remake of this movie could be done, but the creatures, if shown, would have to be uglier and more repulsive than has been done with similar-sized creatures in Gremlins, Ghoulies, and similar movies. Glaring red eyes (not in the original movie, but associated with, say, the Amityville Horror) from the darkness has a horrific shock effect, even filth-dripping bloody cloaks like the Jawas wear (and the dwarfs on Phantasm) might temporarilly shield them from the light, but a few disrobed scenes could be done as well. I still think that the actual sightings of the creatures should be brief, leaving much to the imagination as the original movie did. But in the brief seconds they are bare and exposed in the flashlight beam (before inexplicably retreating and escaping), something along the line of ghoulish, putrid, decomposing monkeys, nastily clawed and with horribly rotting skull-faces and rotting teeth, rapidly and evily putrefying and decomposing in the light, would be in order.
If one should attack (the handyman, for instance), the attack should be as ferocious as the African doll scene on Trilogy of Terror (1975). A scene like in Gremlins, with Sally actually confronting some of the creatures, would be a nice touch throwing some of the hideous things in blenders or microwaves might be in order, though little identifiable evidence would remain (just an extremely foul, putrid, nasty mess)of what the creatures were before being destroyed. Horror writer H.P. Lovecraft typically had his Mythos creatures putrefy to almost nothing when their bodies were (temporarilly) killed. Even light could make these three creatures explode. Glaring eyes, weird sounds, an unbearable, unidentifiable stench in the basement, would be other horror elements. Substances and damage about the house might add to the physical evidence without giving away the full reality.
A remake might want to show the creatures as capable of some type of physical, sleep- or sexual assault (incubi) as well, as such have been suggested on the movies Poltergiest and Amityville Horror. This makes them far more threatening than their merely pulling off ash trays from end tables. Believing one's self to be sexually assaulted in the dark or while half asleep, while these creatures are in immaterial form would add a new dimension to the horror of what the victim is experiencing.
But a remake ought to follow the same storyline, with the same end result.Just a few grosser and more interesting details along the way.
Being kidnapped and taken away is a fate worse than death, and is probably the deepest-pitted fears of ghosts, aliens, boogie-men, etc. The entity does not want to kill us (a mere thug could do that), rather it wants to take us away forever for its own purposes.