No matter how phantasmagorical an extraterrestrial or an alien is in the movie flicks, in books and even in our imagination it always has the common earth-like traits: it has limbs (one or many), it has a mouth (one or many), it has eyes, ears and all that stuff that pretty much sums up the functions we have to perform here on earth. The same goes for the supernatural sightings. A ghost often looks like a human, an animal, an object we already know of, or sometimes even a plant. Of course, sometimes they are invisible so there is no need to give them an appearance, like in The Entity.
Most aliens and ghosts also have humanlike emotions, and if they dont manifest emotions, they are depicted as zombies. But what if there is an existence with no need of time, space and dimension? These, again, are coordinates easily understandable by humans, and Im sure there must be infinite coordinates were not aware of. Again, maybe there are no coordinates to define and pinpoint a particular condition/circumstance.