The dog adopted little opossums who lost their mother. And now the mom has to carry little babies on the back. The matter is that this is how opossum mother transports her children. There is no mom but their instinct makes the babies do the same. They try to behave in a usual way with their new mom. The dog does not mind. The dog became a mother to many opossums. She even feeds them with her milk.
The babies are satisfied with their ride. At least they look actually comfy. Despite this, this is incredible!