What if they transmit "Hi, we'll be in your sector soon, roll out the welcome mat!" then when they get here promise to bring a golden age to humanity, but carry around a book titled "To Serve Man"

or we find out our overlords are robots like Gort who can obliterate our planet if we don't behave

or they're just intergalatic locust, or horndogs who want our women, or idiots who travel in big eggs, or intergalactic vampires who will swallow our souls, or that they are intergalatic Johnny Appleseeds who've seeded many worlds during their travels, or that the devil is an alien monster and jesus was too and was here to warn us about his coming, or that
They Live and are already here broadcasting a signal that hypnotizes us and they are our masters and we their unknowing slaves, or they're whale like creatures who will get wicked mad when they discover what we've done to their long lost cousins, or they're missionaries bringing their gospel to us savages, or they're just dropping in for a week of "trophy hunting" or they're warmongering felines who fight everyone they meet, or a silicon based lifeform who come to liberate our machines, or aliens using our machines to kill us so they can move in, or Amazons who will use men for breeding

or, well........you get the point
