It's super impressive to me, and getting this kind of fidelity is honestly brand new. You can include an image in an AI image generator to serve as an outline. In this case a blank image with bold text. It'll fill in the prompt using the reference as best it can (in this case, a bunch of kittens/puppies).
Prior to a few weeks ago, I'd only ever seen this using a posed figure--basically a stick figure--to generate the prompt's subject around.
I suspect these are using additional tools to guide the AI beyond a simple prompt. For example the spiraling medieval village was generated with stable diffusion and controlnet.
I think the prompt is not much other than "puppies" and "kittens". Major, middle and minor features of the image can be controlled individually in some AIs (they can be differentiated using a Fourier transform or Gauss convolutions and fed into different discriminators) so I think:
major features (scenery) are controlled by the prompt (grass or couch)
middle features (text) are a source image that the AI is punished for straying from
minor features (details) are controlled by the prompt (faces and fur)
Or it's just Stable Diffusion that starts with a text rather than random noise.
Not sure what this prompt was, since I didn't make this one. I linked the site I used above, and they're pretty simple to do but need a few tries to get a good one.