The Plantpot Dapperling (Leucocoprinus birnbaumii) is a small, bright yellow mushroom that frequently pops up unexpectedly in indoor houseplants, greenhouses, and potting soil. These mushrooms are toxic if eaten. They contain a unique alkaloid pigment compound called birnbaumins, which causes the bright yellow hue and induces significant stomach irritation, vomiting, and gastrointestinal distress if ingested.