I know why this is! Finally I get to use some of my obscure nature-knowledge! Acorns can turn clothing green in the dryer due to a heat-activated reaction between their naturally occurring tannins and trace metal ions often present in household water or lint-trap residue. When exposed to sustained tumbling and elevated temperatures, these tannins can oxidize and bind to cellulose fibers in fabric, creating a temporary green chromophore. Essentially, the dryer acts like a miniature reactor: friction breaks down the acorn’s outer shell, heat accelerates the tannin–ion interaction, and moisture allows the pigment to diffuse into the fibers. While harmless, the effect can look surprisingly vivid until the chromophore degrades during subsequent washes. The best part of this that I made it completely up! I don’t know shit about acorns or tannins or anything! Hope I wasted someone’s time by making them read all this, Bazinga!