Billy is a minor character in The Loud House.
He first appears in "Two Boys and a Baby". Lincoln and Clyde mistakenly bring him back to Lincoln's house believing that he's Lily. After discovering that they took the wrong baby, they manage to return to the park and swap Billy for Lily before his father drives away.
Billy looks like Lily, except that he has a tall, yellow, and poofy tuft of hair. He only wears a diaper.