Encyclopedia SpongeBobia
Encyclopedia SpongeBobia

"Mermaid Man and Barnacle Boy IV" is a SpongeBob SquarePants episode from season 3. In this episode, SpongeBob plays with Mermaid Man's shrink ray on his utility belt, but doesn't know how to turn things back to normal size.



Barnacle Boy and Squidward arguing.

In the opening, Mermaid Man and Barnacle Boy are entering the Krusty Krab for lunch, but Squidward and Barnacle Boy have an argument. Squidward, unimpressed with the duo's heroic career, casually mocks them, causing SpongeBob to realize they are in the restaurant and go into an excited frenzy, eagerly requesting their autograph. The heroes run away from him, accidentally leaving Mermaid Man's belt inside. SpongeBob finds it and tries to give it back, but they drive away in the invisible boatmobile before he can do so.

SpongeBob decides to wear the belt and play with it, thinking that he could hold on to it until after work. He discovers the "Small Ray" and starts shrinking the items in the kitchen. At the register, Squidward is suddenly startled by the commotion in the kitchen, which causes him to mess up a customer's order by accident, resulting in a punch in the face. This prompts Squidward to enter the kitchen and ask SpongeBob where the ruckus is coming from, only to see almost everything shrunken. Squidward at that moment discovers that SpongeBob has acquired Mermaid Man's belt. Assuming that SpongeBob has stolen the belt, Squidward plans to do the right thing and call Mermaid Man in order to inform him of the situation. Worried that his reputation with the heroes will deteriorate, SpongeBob panics and shrinks Squidward with the belt after SpongeBob fearfully tells Squidward that if Mermaid Man finds out, he will be kicked out of his fan club for good. Squidward demands SpongeBob to return him to normal size, but he has no idea how. Due to the belt's complicated and excessive features, he instead accidentally puts Squidward through increasingly ridiculous and excruciating torments. Squidward suggests getting Mermaid Man's help, but SpongeBob still refuses, stating someone else must be able to help him and not wanting Mermaid Man to find out.

"I wumbo, You wumbo, he she me... Wumbo"

SpongeBob goes to Patrick for help, to no avail. Patrick mistakes Squidward for an action figure and starts playing with him, even after being told that he is the real Squidward. Patrick then suggests turning the "M" upside down, setting the belt to W for "Wumbo," a meaningless term seemingly coined by Patrick. SpongeBob questions the existence of this word, but Patrick responds by conjugating "Wumbo" and combining it with a handful of other suffixes. SpongeBob is finally convinced by this idea and decides to test it out, but then he accidentally shrinks Patrick. Squidward orders SpongeBob to take him and Patrick to Mermaid Man for help, but SpongeBob still refuses as he does not want Mermaid Man to find out, and places him and Patrick in a jar. Seconds later, citizens start coming to and greeting SpongeBob, prompting him to shrink them so that they cannot tell Mermaid Man that he has gained possession of the belt.

Eventually, SpongeBob has shrunken everyone in Bikini Bottom and crams them all into the jar. When his mother tells him he needs to admit his mistakes, he then realizes he shrunk Mermaid Man and Barnacle Boy as well, and he tearfully apologizes to them. Mermaid Man accepts his apology and trudges through his senility to remember a story about the first time he used the belt, until everyone interrupts him and demands that he tell SpongeBob how to return them to normal size. After thinking for a moment, Mermaid Man asks SpongeBob if he set the belt to "Wumbo," which makes everyone realize that Mermaid Man does not remember how to restore them to normal size either.

The citizens then form a mob and venture into SpongeBob's body, then begin assaulting his internal organs and bones. This goes on a for a while until everyone says aloud that SpongeBob is too big to be destructible, which gives him the idea to shrink Bikini Bottom before shrinking himself.

The citizens are pleased with this, as they see no discernable difference from their previous lives to living in a miniature Bikini Bottom. As the citizens celebrate, a bus pulls up and Plankton steps out, returning to Bikini Bottom from a vacation. He is surprised that the city is now smaller than him as the episode ends.





 ) Production music
 ) Original music
 ) SpongeBob music

  The Lineman - Sam Spence [Title card]
  Hawaiian Link (B) - Richard Myhill [opening]
  Caped Crusader - David Farnon [Mermaid Man and Barnacle Boy enter the Krusty Krab.]
  Tympup A - Sammy Burdson, John Charles Fiddy ["Will this cover it?"]
  Steel Licks 9 - Jeremy Wakefield [Barnacle Boy pays.]
  Steel Licks 10 - Jeremy Wakefield ["I'm shaking."]
  On Fire - Gregor F. Narholz ["Must get autograph!"]
  The Lineman - Sam Spence [Mermaid Man and Barnacle Boy run from autograph hound SpongeBob; Mermaid Man forgot his belt.]
  Awe Zing - Nicolas Carr [Close up of "M"]
  Friendly Aliens (B) - Ron Goodwin ["The emblem of submersible justice."]
  Comic Walk - Sidney Torch ["I could just hold onto it until after work."]
  ? Vibes - Nicolas Carr [SpongeBob giggles]
  The Tip Top Polka/The Cliff Polka - Chelmsford Folk Band ["Here's your shake, sir."]
  Tomfoolery - David Snell [SpongeBob shrunk everything.]
  Dramatic Climax - Mike Sunderland [Squidward demands to be returned to normal size.]
  12th Street Rag - Sage Guyton, Jeremy Wakefield [SpongeBob zapping Squidward]
  Lovely Scenery C - Mladen Franko ["No! I can't let you do that!"]
  Springtime for Lovers - Len Stevens ["He'll find love one day."]
  Steel Licks 1 - Jeremy Wakefield [W for Wumbo]
  Dramatic Impact (3) - Ivor Slaney [Patrick has shrunk.]
  Tympup A - Sammy Burdson, John Charles Fiddy [Patrick has shrunk.]
  Dramatic Impact (2) - Ivor Slaney ["No! He can never find out!"]
  Steel Licks 10 - Jeremy Wakefield ["You know what's funny? My pickle started out in a jar, and now it's in one again!"/"It's like a pun or something. Heheh."]
  Where Danger Lurks - Ronald Hanmer [SpongeBob shrinking everyone]
  Lonely on the Beach - The Hawaiian Serenaders, Jan Rap ["SpongeBob, you need to admit your mistake."]
  The Lineman - Sam Spence [Everyone attacks SpongeBob.]
  Harp! - Nicolas Carr ["I've got it!"]
  Sunny Samoa - George de Fretes, Jan Rap [ending]



  • "Mermaid Man and Barnacle Boy IV" was ranked #90 during the Best Day Ever event from November 9–10, 2006.



  • The beginning of the episode brings attention to the similarity between Barnacle Boy and Squidward Tentacles' noses.
  • The episode premiered on Martin Luther King Day during the SpongeBob-a-Thon.
  • This is the first episode where Mermaid Man's belt is purple with a blue "M" instead of yellow with a yellow "M."
  • There is a book based on this episode named The Adventures of Man Sponge and Boy Patrick in What Were You Shrinking?
  • This is the second episode where SpongeBob is wearing a belt covering his clothes throughout most of the episode. The first was "Hall Monitor."
  • This is the third time SpongeBob shrinks. The first time was in "Nature Pants," and the second was in "Big Pink Loser," the latter seemingly at will.
  • "My leg!:" Everyone is squished inside the jar.
  • Patrick's introduction of the term "wumbo" and subsequent explanation has become an internet meme.
  • Despite SpongeBob shrinking everyone in Bikini Bottom, Mr. Krabs, Gary, Pearl, and Karen are not seen, meaning none of them appear in this episode.
  • This is the second episode Plankton appears bigger than the Bikini Bottomites. The first was "Sleepy Time," though it was only a dream.
  • When SpongeBob breaks through the steel wall at the Krusty Krab, he is animated in CGI with cel-shading.
  • After SpongeBob shrinks everyone in town, Patrick is not seen again for the rest of the episode.
  • Initially, in the Indonesian dub, the scene where SpongeBob shrinks Squidward was skipped to running into Patrick due to time constraints and paired with 5-minute ads. However, in later airings, the aforementioned scene plays normally while the scene where everyone beating SpongeBob was omitted instead because the depiction of damaging organs was deemed too violent.[citation needed]
  • When Squidward yells at SpongeBob to stop zapping him with the belt, his animation looks nearly identical to the deleted scene from "Just One Bite" when Squidward bursts into the kitchen after being doused in gasoline and set alight.

It is revealed that the invisible boatmobile is a 1950s Cadillac.

  • The invisible boatmobile is revealed to be a pink 1959 Cadillac in this episode, despite the outline actually being boat-shaped in "Mermaid Man and Barnacle Boy" and "Mermaid Man and Barnacle Boy III."
  • This marks the only episode to date where Margaret SquarePants is seen without her husband.
  • This episode reveals that there is a phone in the kitchen of the Krusty Krab.
  • This episode reveals that Mermaid Man has been fighting crime for over 65 years.
  • When SpongeBob is reaching for the pen, he says "Keyah!," which is the Taekwondo word used when one is about to perform something.
  • SpongeBob cannot get the citizens of Bikini Bottom back to normal, but in "Mermaid Man and Barnacle Boy," SpongeBob mentions a ray gun that made things grow six times their normal size. SpongeBob was so scared, he forgot about it, or it may have been a different tool altogether from the belt.
  • This episode has been paired with different episodes:
  • According to the production code, this was produced as a season 2 episode.
  • This is the second Mermaid Man and Barnacle Boy episode where neither Man Ray nor the Dirty Bubble appear. The first was "Mermaid Man and Barnacle Boy."
    • However, the former was mentioned in that episode.
  • In the scene where various townsfolks are damaging SpongeBob's insides, the English version has Mermaid Man saying, "We've been shrinking for years!" to which Barnacle Boy replies, "But this is ridiculous!" In the Latin American Spanish dub, the line has been changed, and Mermaid Man says, "¿Y tú sabes porqué nos encogimos?" (And do you know why we were shrunken?) and Barnacle Boy says, "¡Ya, no digas tonterías!" (Don't talk nonsense already!)[citation needed]
  • The French dub calls this simply "The magic belt."[citation needed]

Cultural references

  • When Patrick is ranting about wumbo, he mentions wumborama, a reference to Futurama.


  • When SpongeBob is running to Patrick, one can see that the former is not wearing the utility belt in the first shot.

Mr. Krabs' office door is gone.

  • When Squidward enters the kitchen to confront SpongeBob for stealing Mermaid Man's belt and for shrinking everything in the kitchen, the door that leads from the kitchen to Mr. Krabs' office is gone.
  • Even though there are several cars parked outside the Krusty Krab, there are very few customers inside it except for Mermaid Man and Barnacle Boy.
    • When Mermaid Man and Barnacle Boy drive off from the Krusty Krab, all the cars are gone.
  • After Mermaid Man uses the invisible boat alarm and says "There she is," he is just holding his pants, but when he gets to the boat, he is wearing clips on his pants, which he was not seen putting on.
  • The aforementioned clips holding up Mermaid Man's pants change colors between shots.
  • When SpongeBob gives the Krabby Patty to the cockroach, the slots on his spatula disappear.
  • In South Korea, this episode was banned due to the flashing lights to cause the viewers seizures.
  • Mermaid Man is clearly overweight, but his pants are still somehow too big when he does not wear his belt.
  • When SpongeBob shrinks Sandy, Squidward and Patrick's eyes are black.
  • SpongeBob has difficulty closing the jar with everyone trying to fit in it, but when Mermaid Man mentions setting the belt to "Wumbo" and everyone yells "What?!," it appears that they do not quite fill up the jar to the top, and he has plenty more room. This also happens when he cries "You don't understand!"

Barnacle Boy's eyes are missing.

  • When Barnacle Boy says, "But this is ridiculous," his eyes are missing for a split second.
  • In the aforementioned shot where everyone yells, "What?!," when the screen shakes, the background is not big enough, which causes some bits of white to be shown. The effect is at 60 Hz, as opposed to the 24 Hz animation itself, so this error clearly arose in post-production.
  • In some shots of when the townspeople are beating up SpongeBob's inside, SpongeBob has bones and organs. However, SpongeBob is an invertebrate.
    • However, SpongeBob does not have any organs, or bones for that matter, in "Slimy Dancing."
  • When everyone pops out of SpongeBob, Sandy's head is missing.

The dining room wall with a bluish-gray color.

The dining wall back in its original colors; SpongeBob's buck teeth are also missing.

  • When SpongeBob shrinks himself, Mermaid Man's belt is changed into his normal pants.
  • When SpongeBob bursts through the wall overhearing Squidward saying "Mermaid Man and Barnacle Boy," it is blue in the first shot. After SpongeBob grabs the pen, the wall is back to its original colors in the second shot.
    • Additionally, when the walls are in their original colors, SpongeBob's buck teeth are missing.
  • Plankton is shown as taller than the town at the end of the episode. However, when SpongeBob is shrinking the people of Bikini Bottom, their sizes in the pickle jar seem to be around Plankton's actual height. Plankton should have been around the same size as the rest of Bikini Bottom's residents after the shrinking, not twice the height of the skyline.



SpongeBob Learns About Wumbo! 🦸‍♂️ "Mermaid Man & Barnacle Boy IV" 5 Minute Episode


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