Duck is one of the four major characters from the in-universe parody series Cow Duck Avocado Mantis. She is meant to be the alternate version of Goat.
Unlike Goat, Duck is considered the artist of the group and can DJ by playing the turntable.
Duck wears the same clothing as Goat: a white tanktop, black skirt and black "Mary Jane" shoes. However, contrary to Goat, she has a bill and no horns, since she is a duck.