Billy the Snail is a snail who only appeared 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 but on his shell there are no dots, just red lines like Gary's, just thinner. He has a green-blue skin, black hair and blue eyes with a brown leash. Billy the Snail can be only seen in the hit series "The Adventures Of Gary The Snail." He is the voice by Adam West.
- When he says "meow", instead of saying it like a cat (like most snails), he is voiced by a man.