Billy may refer to:
- Billy (brown fish) - A fish that appears in the episode "Squirrel Jokes."
- Billy (lime fish) - A fish that frequently appears in the Krusty Krab.
- Billy (purple kid) - A child that first appears in the episode "Friend or Foe."
- Billy (blue fish) - The birthday boy in the episode "Krusty Katering."
- Frankie Billy - An olive green fish.
- Billy the Snail - The pet snail of Brad, as seen in the episode "Gary in Love."
- Billy the Orca - A killer whale that appears in the episode "SpongeGuard on Duty."
- Billy Fishkins - A fish that appears in the episodes "The Chaperone" and "Don't Look Now."
- Baby Billy - The baby of Shubie that first appears in "Goo Goo Gas."