Forget all that stuff about them being natural enemies. Domestication has it licked.
It’s natural for a kitten and a puppy to play together. Either one of them could always run away. And at the end they cuddle up for a nap.
We praise the Creator who gave us this.
I’ve seen this situation several times. Usually, it has been with one mother animal and a baby one, but not always.
Years ago, I had a very nice tomcat. A friend got a Pomeranian puppy and the puppy grew up playing with the tomcat. They would wrestle, and a good time was had by all. A couple of years later, I got a second cat, who had lived on the street for a year, and saw dogs as a threat. The first time she saw the tomcat and the Pomeranian wrestling, she ran to them with great concern, and then looked back at me, apparently wondering how I could tolerate such a travesty.
The years passed, and after the tomcat passed away, my other cat still saw the Pomeranian as suspect, and was somewhat demonstrative about her distrust. However, occasionally they would touch noses when they first met, and from that point, it was all feline theater. 🙂