In 2019, I made a heap of roughly 300,000 curves and colored them blue and purple. They looked enough like Sulley from Monsters, Inc. that I called the image The Unsullied.
It was a crossover joke with Game of Thrones. More importantly, or at least more defensibly, it was a test of the new RenderMan for Houdini plugin shipping with RenderMan 22.5.
The curve system was built procedurally in Houdini, starting from an Entagma tutorial by Moritz Schwind. The rewritten plugin made it practical to send the curves directly to RenderMan. That matters when there are 300,000 of them. Manually arranging the hair was not seriously considered.
Each curve carried primitive variables that controlled its color. Those values fed RenderMan's Marschner hair shader, the same kind of physically based hair model used in Pixar production. One area light and a Daylight shader lit the scene; RenderMan's uni-directional path tracer handled the light transport.
The useful part was not merely that RenderMan could render the curves. I could work on the look interactively inside Houdini, changing the hair shader and seeing the result without turning the process into an export-and-wait ceremony.
The less useful part was realizing that turquoise and violet hair comes with prior associations.
Pixar used the image with the RenderMan 22.5 release, and Ian Failes later asked me to explain it for befores & afters. The release needed an image that showed what the new Houdini workflow could do. Apparently it also needed a joke that required familiarity with two unrelated television properties.
This is one of the things new tools are good for. They remove a technical obstruction, and almost immediately somebody uses the opening to make something the tool's designers could not have specified in a feature list. In this case: a procedural hair system, a production renderer, and a fairly bad pun.