You’ve seen him. Maybe you didn’t know his name, but you’ve definitely heard the scream. "My leg!" Fred the Fish is probably the most famous background character in animation history, yet he’s just one of dozens of recurring SpongeBob side character fish that keep the show's world from feeling empty. These aren't just random drawings used to fill space. They have lives. They have names. They have specific voice actors who have stayed consistent for over two decades.
It’s honestly kind of wild when you think about it. Most cartoons swap out background extras every few episodes to save on design costs or just because the artists get bored. Not SpongeBob SquarePants. Since 1999, the production team at Nickelodeon has maintained a "model sheet" of specific fish—like Tom, Harold, and Nat Peterson—to ensure Bikini Bottom feels like a real, functioning town.
Why the SpongeBob Side Character Fish Matter More Than You Think
Bikini Bottom functions because of its citizens. Without the crowd, the Krusty Krab is just a hollow shell with a cheap crab and a fry cook. The presence of these specific fish provides a sense of continuity that most kids' shows lack. When a riot breaks out, it’s usually the same group of guys flipping over tables.
Take Tom, for example. You know him as the "Chocolate!" guy from the episode Chocolate with Nuts. His official name in the production notes is actually Tom, but fans spent years just calling him the Chocolate Fish. He’s been a recurring background element since the pilot, often appearing as a customer or a disgruntled pedestrian. What makes Tom interesting is how his personality shifts from a generic citizen to a localized maniac depending on the plot's needs. He represents the "everyman" of the sea, usually frustrated by the chaos SpongeBob and Patrick cause.
Then there’s Harold. Not to be confused with Harold SquarePants (SpongeBob’s dad), this Harold is a blue fish with an orange shirt. He’s the one who famously yelled, "Big! Scary! Pink!" in the episode Krusty Krab Training Video. He’s often used for comedic exposition. He’s also the guy who gets his drink spilled or ends up in a headlock during a bar fight at the Salty Spitoon.
The "My Leg" Guy and the Legend of Fred
Fred isn't just a meme. He is a pillar of the show's sound design. voiced by Mr. Lawrence (who also voices Plankton), Fred’s "My leg!" catchphrase started as a simple running gag but evolved into a full-blown character arc.
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In the 2018 episode titled My Leg!, the show finally gave the fans what they wanted: a deep look into why Fred’s leg is always breaking. It turns out, he loves the hospital food and the attention he gets from the nurses. This meta-commentary on a 20-year-old background gag is exactly why the SpongeBob side character fish have such a massive following on social media and Reddit. People love the lore.
The Anatomy of a Background Fish
- The Character Design: Most of these fish utilize a palette-swapping technique. For example, the "Incidental 37" model might be green in one scene and purple in another, though the show has gotten better at keeping them consistent lately.
- The Voice Talent: Dee Bradley Baker and Mr. Lawrence handle about 80% of these roles. If you hear a fish screaming in the distance, it’s probably Dee.
- The Names: Most names come from the storyboard artists or the original "Incidental" numbers assigned by the character designers like Derek Drymon and Stephen Hillenburg.
Nat Peterson and the Evolution of the "Hater"
If Fred is the victim and Tom is the maniac, Nat Peterson is the skeptic. Nat is the yellow fish often seen driving a boat or eating at the Krusty Krab. He was famously the focus of the "Plankton's Regular" episode, where Plankton tries to win him over as a customer.
Nat’s role is usually to react to the absurdity of the main cast. He’s the guy who looks at the camera with a "you've got to be kidding me" expression. He represents the audience's logic. When SpongeBob does something physically impossible, Nat is usually there to provide the reality check.
Interestingly, Nat has a bit of a complicated history. In some early episodes, he was used interchangeably with other yellow fish models, but by Season 3, his identity solidified. He’s even had a family shown on screen, which adds a layer of depth you don't usually see for a character who rarely has more than two lines of dialogue per appearance.
Scooter and the Surfer Tropes
We can't talk about the citizens of Bikini Bottom without mentioning Scooter. He’s the purple fish who sounds like a 1960s surfer. "Dude, he's making a guitar!"
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Scooter is unique because he actually "died" in the episode Bubble Buddy—well, he was buried in the sand and drowned by the tide, then came back as an angel—only to reappear in the next scene as if nothing happened. That’s the beauty of these characters. They are indestructible icons of the show’s logic. They exist to suffer for the sake of a joke and then reset for the next episode.
Notable Background Fish You Definitely Recognize
- Frank (aka Muscular Fish): Often seen at Goo Lagoon or the gym. He’s the one who gets "tanned" into a crisp or tries to lift heavy weights.
- Old Man Walker: The tiny, hunched-over fish who is constantly being stepped on or ignored. He’s a classic "grumpy old man" trope.
- Sadie Rebeccas: One of the few recurring female background fish, often seen shopping or reacting in horror to Patrick's antics.
The Cultural Impact of the Background Cast
Why do we care? Why are there thousands of YouTube compilations dedicated to "Every Time Fred Says My Leg"?
It’s about the "lived-in" feeling. Shows like The Simpsons mastered this with characters like Comic Book Guy or Bumblebee Man. SpongeBob did it with fish. It rewards long-time viewers. When you see a fish like Incidental 41 (the one with the red tie) walk into a scene, you feel a sense of familiarity. You know how he’s going to react.
Social media has amplified this. TikTok and Twitter are filled with "Which Bikini Bottom citizen are you?" quizzes. These characters have become a shorthand for specific human emotions—frustration, confusion, or just wanting to eat a Krabby Patty in peace.
The Business of Being a Background Character
From a production standpoint, having a set of established side characters is a stroke of genius. It creates a brand identity. You can't just draw any fish; it has to look like a SpongeBob fish. The round eyes, the slightly protruding teeth, the lanky fins—it’s a specific aesthetic developed by Hillenburg, who was a marine biologist.
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This consistency also helps with merchandising. There are action figure sets specifically for the "Background Fish." People actually buy them. They want the "Chocolate!" guy on their shelf next to SpongeBob and Squidward. It’s a testament to the show's writing that even the "nobodies" are "somebodies."
Where to Look for These Characters Now
If you’re watching newer episodes or the spin-offs like The Patrick Star Show or Kamp Koral, keep your eyes peeled. The animators are leaning harder into the fan service. You’ll see Fred more often. You’ll see Tom’s obsession with chocolate referenced in the background.
The legacy of the SpongeBob side character fish is a reminder that in good storytelling, no detail is too small. Every person in the crowd has a story, even if that story is just that they really, really need to go to the hospital because their leg is broken.
Next Steps for Fans and Collectors
To truly appreciate the depth of these background characters, try these specific actions:
- Watch for the "Model Swaps": Re-watch Season 1 and Season 2 back-to-back. Notice how certain fish like "Incidental 48" (the orange one with the white shirt) start to appear more frequently as the show finds its rhythm.
- Check the Credits: Look for the voice cast. You’ll see that the same four or five people provide almost all the voices for the background citizens, which is why the "vibe" of the town never changes.
- Deep Dive into the Wiki: The SpongeBob Encyclopedia has meticulously documented every single appearance of these fish, often categorizing them by their "Incidental" number. It’s a goldmine for trivia lovers.
- Identify the "Big Three": Practice spotting Fred, Tom, and Nat in every crowd scene. Once you see them, you can't unsee them. They are in almost every major event in Bikini Bottom history.