there's a conspiracy theory of sorts that's been passed around for years that goes something like this: demons are going to invade the earth and take over sometime in the near future. pop culture's infatuation with UFO's and aliens is explained by demonic influence of the media, either direct or indirect, and is being spread to 'normalize' the idea of aliens so that when the earth's new demonic overlords show up in full physical form everyone accepts them as natural.
this is usually explained as some kind of weird interpretation of Revelation & other eschatological prophecy, as though the Antichrist will be a demon masquerading as an alien and by this he'll become accepted as ruler of the whole world. by mentioning a book and some characters in the Bible, this story gets associated with Christianity, but it's in no way a 'church' doctrine and doesn't come from scripture, even though one way or another you may hear it from people who take the name 'Christian'
i've never heard any actual 'church' teach anything like this, or ever heard anyone ever give a sermon that ever mentioned aliens or UFO's at all, period, other than to briefly make an analogy with Christians being 'aliens and strangers' in the world in a metaphorical sense.
now that you mention it you might want to ask some Mormons, since they believe God is an alien from another planet, and is just one of an infinite line of god-creatures each with their own planet and people to be god over, and that they themselves ((if they're especially holy)) may eventually become gods in exactly the same way each with their own planets to be gods over, having babies for all eternity who may eventually ((if they're especially holy)) get their own planets, and so on. they'll say of course, that that's not what 'becoming exalted' is fundamentally about to them, but, that is the doctrine. or at least some of their prophets are false, heh - it's one or the other.
or ask a scientologist, if you really want to get into the weird.