Swap/Blue is a skeleton from Underswap. He always wears his baby blue bandana, a gift from his father, Gaster. His twin brother is Papyrus, another skeleton. He wears grey armor over a white shirt, a black belt, black baggy sweatpants with white stripes, and blue boots. Blue gets upset when things don't go as planned and when others annoy him. His friends are Dream, Ink, Error, and Alphys.