The same is true of the aliens in Star Trek . You can look at the credits for each show, and you will find that every alien is played by a human actor. I hope I haven't ruined some Trekkie's day by pointing this out. The same way we would relate to an appearance of Capser the Ghost or Mickey Mouse. The question is meaningless, since we have no reason to believe that such beings exist anywhere in the universe.
Aliens exist only in mythology.
My categorical statement denying ETI probably sounds surprising. It has become fashionable to believe in at least the possibility of sentient alien races. This is one of the wild hopes of the New Age Movement. In her autobiographical book Out on a Limb, Shirley MacLaine tells us that in one of her former lives, her husband had been an ambassador for the Lost Continent of Atlantis to the UFO people. Ms. MacLaine has now been chosen by these aliens to bear their message of a New Age.