When it comes to baptizing an alien, there’s them and there’s us. If it is only us, then the alien lets us examine the depths of God’s inclusivity and his exclusive love for all individual human beings, in much the same way as the pope.
But if an authentic flesh and green-blooded alien shows up, then the focus shifts necessarily from us to the alien. Then we ask what is asked of each of us: What are his beliefs, his desires; what is his declared need for baptism?
In Michael Flynn’s novel Eifelhem, aliens, looking very much like five-foot ten-inch grasshoppers, find themselves stranded in plague-ridden 14th century Germany. More than a few of them are engrossed by human behavior, shaped by faith and displaying an elemental kindness. This was an experience, well, alien to their own society. They seek out the priest for baptism.
They become the alien “us” we seek, confirming the better qualities of human life with which we flatter ourselves. The pope’s Martian becomes the foil against our inclination to self-centeredness when confronted with the unbounded love of God that can bridge even light years.