Jeff Koons is an artist who regularly runs into plagiarism lawsuits. The contrast of the outcomes of two lawsuits helps illustrate the difference between plagiarism and transformative appropriation.
The first example of this from the Roger v. Koons suit:
Koons exactly copied Roger’s personal photograph in a sculpture, which sold for a high price. Roger wasn’t credited or given any of the profits. He lost the lawsuit on the grounds that his “parody” argument was weak and that the work was not transformative enough to qualify under a free use creative license.
Meanwhile, this painting by Koons was deemed transformative, because even though he copied another photographer’s work, the collage element and possible cultural statement fell under free use in the eyes of the court. There’s a thin line (at least legally) between appropriation and outright plagiarism, and Jeff Koons walks that line even if he often crosses it in some people’s eyes.
Images from: https://www.owe.com/resources/legalities/30-jeff-koons-copyright-infringement/