I should've been clearer, really. What made me feel the "magic" was not prompting Stable Diffusion. It was letting it iterate on art I had already done.
I did a lot of 3D-rendered illustration back in the 1990s and early 2000s, necessarily low-polygon stuff, but things that were supposed to be life-like scenes, with tons of textures, that took a very long time to render. Including what may have been the first and only children's book illustrated with Infini-D on a Mac IIsi.
So, feeding these old renderings into StableDif with 75% bias toward the original image and a couple of basic prompts, produced results that blew my mind. It was like seeing what my illustrations could have been if I'd had a team at Pixar Studios refining them. In the sense that it was still my character art and my creation, totally recognizable, but polished and refined to a level that would have been unimaginable in 1997.