"Mermaid Man and Barnacle Boy IV" is a SpongeBob SquarePants episode from Season 3. In this episode, SpongeBob plays with Mermaid Man's secret utility belt.



Barnacle Boy and Squidward arguing.

In the beginning of the episode, Mermaid Man and Barnacle Boy are entering the Krusty Krab for lunch, but Squidward and Barnacle Boy have an argument. Upon realizing this, SpongeBob goes into an excited frenzy and eagerly requests 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 caused him to mess up one of the customers' order by accident, which results in a punch in the face. This prompts Squidward to enter the kitchen to see everything having been shrunken. Squidward at that moment discovers that SpongeBob has gained possession of 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 and thus get revenge. Worried that his friendship with the heroes will deteriorate, SpongeBob shrinks Squidward with the belt to foil his plan. Squidward demands SpongeBob to return him to normal size, but he has no idea how to. Due to the belt's complicated and excessive features, he instead puts Squidward through many increasingly ridiculous and excruciating feats. 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.

"A Squidward action figure!"

SpongeBob goes to Patrick for help, to no avail. Patrick mistakes Squidward for an action figure and starts playing with him, even after realizing that he is the real Squidward. Patrick then suggests turning the "M" upside down, setting the belt to W for "Wumbo," which results in Patrick coining the term. SpongeBob questions the validity of this, but after Patrick responds by stating the many uses of "Wumbo," SpongeBob is 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 doesn't 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 his belt.

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

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 goes into 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 know how to unshrink them either.

The citizens then form a mob and venture into SpongeBob's body, then begin assaulting his internal organs and bones in a violent manner. This goes on a for a while until everyone realizes that SpongeBob is too big to be destructible, which gives the latter 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. 





 ) Associated 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 8 - Jeremy Wakefield [Barnacle Boy pays.]
  Steel Licks 9 - 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 9 - 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.



  • Barnacle Boy and Squidward Tentacles share the same nose.
  • The episode premiered on Martin Luther King Day during 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's 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 shirt and tie throughout most of the episode. The first was "Hall Monitor."
  • This is the second episode where a tiny version of Bikini Bottom is shown. The first is "Sandy, SpongeBob, and the Worm."
  • This is the third time SpongeBob shrinks. The first time was in "Nature Pants," and the second was in "Big Pink Loser."
  • "My leg!:" Everyone is squished inside the jar.
  • Despite SpongeBob shrinking everyone in Bikini Bottom, Mr. Krabs, Gary, Pearl, and Karen do not appear in this episode.
  • This is the second episode Plankton appears bigger than the Bikini Bottomites. The first is "Sleepy Time," though it was only a dream.
  • This episode has SpongeBob's CGI cell-shaded appearance when he breaks a steel wall at the Krusty Krab.
  • After SpongeBob shrinks everyone in town, Patrick is not seen again for the rest of the episode.
  • Initially, in Indonesian version, 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 organ damaging scene was considered as a violent scene.

It is revealed that the invisible boatmobile is a 1959 Cadillac.

  • The invisible boatmobile is revealed to be a pink 1959 Cadillac in this episode.
  • 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.
  • In the Monday Knight Slimetime marathon, this episode was paired with "I Had an Accident."[2]
  • According to the production code, this was produced as a season 2 episode.


  • 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 a lot of cars parked outside the Krusty Krab, there are no 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 holes on his spatula disappear.
  • In South Korea, this episode was banned due to the flashing lights to cause the viewers seizures.
  • Mermaid Man is overweight, but his pants do not fit him 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.
  • 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.
  • 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.
  • 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 equal with Plankton's actual height. In reality, Plankton should have been around the same size as the rest of Bikini Bottom's residence after the shrinking, not 5 times taller.



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


Mermaid Man and Barnacle Boy (VE)
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