Billy is a snail who just appears in the episode Gary in Love. His owner is called Brad. After Billy came back from going for a walk with Brad, he becomes Mary's new boyfriend, which makes Gary and Mary's Ex-Boyfriend very sad.
Billy has a pink-colored shell like Gary. Unlike Gary's, it has no dots. It only has a thin red line. Billy has green skin and a blue underside. He has black hair that looks like a pompadour and blue eyes.