I just went down a rabbit-hole, and happily I found the rabbit - an early example of this type of prompt (draw an unusual animal character in a vector graphics language). There is a paper and a 1 hour podcast resulting from a Microsoft evaluation of a pre-release of GPT4. One of the prompts (see pages 4,7,8 in the paper PDF) was to draw a unicorn in TikZ. (I'll leave to the historians the questions of whether this was the first, or whether Simon Willison may have been inspired by this). I remember hearing some of the podcast, and recalled the prompt about balancing on a nail, and the triangle forming the unicorn's tusk; this was clearly a big step beyond choosing the next word and blending images.
https://arxiv.org/abs/2303.12712