It is not impossible that Lucifer's angels (devils) could well appear in the future disguised as aliens. Now you may well ask why this might happen. The possibility of other worlds and intelligent beings on them has been around for a long time. Well before Christ the Pythagoreans had conjured up the belief that the world evolved from atoms. Now if the Earth and mankind evolved then it is perfectly reasonable to assert other such worlds also evolved with their intelligent life we call aliens.
Along came the Christ and the Bible with its revelation of a created Earth, created Man in His image, then Original sin and redemption by Christ the son of God as the second person of the Trinity. We were told all about the afterlife.
Once Christianity began, the assertion that other worlds and other aliens exist was condemned by the Fathers throughout the early centuries. In 748AD, Pope Zachary I declared heretical the belief that stars were suns with similar worlds like Earth around them and that on these bodies are other intelligent beings. In 1459 Pope Pius II rejected the doctrine ‘that God created another world than this one.’ In 1591, Pope Gregory XIII’s Corpus of Canon Law was expanded and included the heresy ‘having the opinion of innumerable worlds.’
‘Other theologians too cited this heresy for centuries. They explained the problem, “we cannot assert that there exist two or many worlds, since neither do we assert two or many Christs [the only begotten son]” Aristotle had insisted that many worlds cannot exist since it would require more than one First Cause.’-- Prof. A. Martinez.
Then along came Copernicus and his heliocentrism one of the same Pythagorean heresies condemned in the early Church. In the year 1600, Giordano Bruno was burned at the stake for his heresies, one of them being that there are many other worlds like ours that have life on them, intelligent-beings now called aliens, a belief that for Catholicism must involve other Adams and Eves, other alien original sins and even other Christs.
Kepler also put out his belief in Aliens.
‘In the latter half of the sixteenth century these evolutionary theories seemed to take a more definite form in the mind of Giordano Bruno, who evidently divined the fundamental idea of what is now known as the “nebular hypothesis,” [the evolution of their solar system, resurrected in 1755 by the German philosopher Immanuel Kant and modified in 1796 by Pierre Laplace]. Yet within the two centuries divided by Bruno’s death the world was led into a new realm of thought in which an evolution theory of the visible universe was sure to be rapidly developed.’
In 1820, Pope Pius VII allowed this evolved heliocentric world to be believed by Catholics. From then on NOTHING was forbidden about Big Bang evolution. Now as we said, if the Earth and man evolved then why not other worlds and aliens. Totally forgotten were the alien heresies condemned in the early Church as well as those that Bruno was burned at the stake for.
Thus began the acceptance by churchmen that aliens may exist even though that would make the Genesis Catholic faith alone redundant. In 2009, the Vatican had begun hosting conferences with scientists and religious leaders discussing the implications for religion and human consciousness if extraterrestrial life is found on ‘numerous worlds.’ One statement was that aliens would be part of God’s Creation so would be regarded as our ‘extraterrestrial brothers.’ Here is another:
‘Father Funes described the discovery as ‘great news.’ Writing in the Vatican’s daily newspaper L’Osservatore Romano, he said: ‘Our galaxy contains more than a hundred billion stars. ‘Considering the number of exoplanets discovered, it seems that the vast majority of stars in our galaxy, at least potentially, can have planets where life could develop.’ He said that if there is intelligent life found on another planet, he does not see it as a contradiction to the Christian faith. He said: ‘The Bible is not a scientific book. If we look for scientific responses to our questions in the Bible, we are making a mistake. It is just over 380 years since the Catholic Church condemned Galileo for arguing that the Earth was not the centre of the universe. But it seems the Vatican has relaxed its view of mankind’s place in the cosmos and even believes there may be intelligent alien life out there. Astronomers at the Vatican Observatory, which has been studying the heavens since 1582, have said discoveries of new Earth-like planets have strengthened their belief that there could be life on other planets.’ ---Mailonline, 8th Feb, 2018.
‘LOOKING FOR ALIENS,’ by M. Wertheim. ‘Throughout his astronomical career, Father George Coyne, senior scientist at the Vatican Observatory Research Group, whose work has inadvertently dovetailed with our growing desire for extraterrestrial contact, a subject about which he remains optimistically equivocal…. Roger Angel says: “Before, you could only speculate about extraterrestrial life. Now we’re at a point where we can make telescopes with which we can actually go looking for life.” Looking out at the telescopes arrayed around us, Fr Coyne suggests that we might view stars as God’s sperm. Every sperm has the potential to produce life, he says. Father Coyne is confident that we are not alone. As a priest and a scientist, the marvel for him is the universe itself.’ -- Science & Spirit website.
There is now a Society of Catholic Scientists who in June 2021 held a three-day conference on ‘Extraterrestrials, AI, and Minds Beyond the Human.’
Finally, if the devil got a bunch of demons to arrive in some craft saying they were aliens, where do you think that would leave the credibility of Genesis. With churchmen now prepared to accept their existence and sightings being reported as alien space ships, the scene is now set for Satan to make it happen. Pope Francis said recently he would baptise a Martian if asked, making a mockery of the sacrament that affects only the descendants of Adam and Eve.. He at least has no problems getting Martian aliens into heaven.