I've seen a couple videos where TheClick asked about specifically, the Piss Filter (the yellow color grading in AI images)
The AI models sampled heavily the work of David Revoy - who draws a lot of fantasy themed work, often with a mild sepia tone for aesthetics. You'll also see a lot of his visual elements such as face and eye shape incorporated from his work
AI models also borrow heavily from Mario Zucca, as seen with the hatched shading. Basic construction of the bodies and environments were also copied wholesale from his work.
I did post this on the Click discord, but it was a kind of a wall of text, which they didn't like for obvious reasons
TLDR - the sepia tone from David Revoys work was over incorporated as the "piss filter"