Billy Martin appears only as a background character, with "Quest for Ratings" being his first appearance. In "HUMANCENTiPAD", his father is seen, and in "200" he is seen with a woman, possibly his mother. In "Dances with Smurfs", he is seen in a different classroom.
His name is revealed in "Bass to Mouth" in a story visible on Eavesdropper about how he got his hand stuck in his locker and how he thinks it hates him.