Billy may refer to:
- Billy, son of Mable Monica, as seen in "Squirrel Jokes."
- Billy (lime fish), adoptive son of Evelyn.
- Billy (purple kid), a child as seen in "Penny Foolish."
- Billy (Student), he is seen in "Professor Squidward," and in other episodes.
- Billy the Snail, pet of Brad, as seen in "Gary in Love."
- Billy the Orca, a killer whale seen in "SpongeGuard on Duty."
- Billy Fishkins, a fish seen in "The Chaperone" and "Don't Look Now."