Everyone knows that cats and dogs are very different. It's a stereotype for a reason. Dogs wag their tails when they are happy, while cats wag their tails when they are annoyed, overstimulated, uncertain, or very much not happy. The opposite of happy. And that is just the tip of the iceberg when it comes to the differences between them. But that doesn't mean that they cannot bond. In fact, cats and dogs can be best friends.
Under the right circumstances, for example, when cats and dogs grow up together. Or even when they don't grow up together - if a cat is particularly friendly and accepting or if a dog is patient and persistent enough, friendship can bloom between them. In Upset_Nectarine_1281's story, we think that it was a mix of a few things.
The dog in this story was newly adopted. She had been with her new family for barely a month before this kitten came into their lives. She was most likely still adjusting to this new environment herself. And then, out of nowhere, a kitten in need of help shows up in the house too. The kitten is tiny, the kitten is sick, and the kitten is absolutely terrified of this new reality that he has been dropped into. Maybe the pupper could sympathize. Maybe she wanted something to nurse, to care for, to distract her from her own new reality. Either way, despite not growing up together and not knowing the behavior patterns of other cats and dogs, these two bonded through their shared experiences and will stay bonded until the end of their lives.