Song/story -- Mary and Joseph find no room at the inn; the staff treats them haughtily. They return to the stable holding their mule; the animals treat them better than humans had, making room for Mary to give birth, breathing on Jesus to keep him warm
It probably need not be pointed out that the account of Jesus's birth in Luke (the source for all the incidents mentioned) does not say that the staff of the inn in Bethlehem mistreated Mary and Joseph; it merely says there was no room there.
The behavior of the animals in the stable is equally fictitious; the Lukan account not only doesn't mention animals, it doesn't even explicitly mention a stable! We call it a stable simply because it contained a "manger" (though the Greek word, phatne, feed-trough, sometimes extends to mean a stable). - RBW