"Yellow" (also known as The Cowgirl) is a major antagonist and boss encountered in Chapter 5 of Deltarune. Originating as a sentient yellow flower from Asgore and Toriel's wedding bouquet, she takes on a cowboy-themed humanoid form when transformed by a Dark Fountain. Alternatively, the term can refer to Deltarune Yellow, a popular community fan game that reimagines the prequel Undertale Yellow. In Chapter 5, Yellow resides within the Flower Kingdom, specifically patrolling the left side of Flower Castle alongside her romantic partner, Blue. Her design explicitly nods to the Yellow "Justice" SOUL from Undertale. She sports a dark yellow cowboy suit, gold boots with spurs, and a cowgirl hat. Extremely well-meaning but heavily gullible, comedic, and obsessed with stopping individuals she deems "criminells". She is famously involved in a running gag where she experiences existential dread upon realizing she cannot technically be a "cowgirl" because she doesn't own any cows. The party cheers her up by convincing her that since she drinks milk, the cows are technically inside her body.