Mermaid Man and Barnacle Boy IV is an episode from Season 3.
One day Mermaid Man and Barnacle Boy decide to eat at the Krusty Krab. Mermaid Man does not have any money to pay for the food they order. Barnacle Boy asked Squidward for any discount and Squidward got mad at him. Barnacle Boy then paid the money they owe for the food. Squidward got angry and said: Mermaid Man and Barnacle Boy in a negative way. SpongeBob over heard Squidward and tried to find a pen and a paper to get their autograph. Mean while Mermaid Man demonstrates Barnacle Boy how to be big and strong. He removes his belt and his huge stomach was revealed. SpongeBob then ran towards Mermaid Man and Barnacle Boy. They saw SpongeBob coming and Mermaid Man and Barnacle Boy left. Mermaid Man forgot his belt and SpongeBob tries to return it. Mermaid Man and Barnacle Boy try to find the invisible boat mobile and went home. SpongeBob unfortunately did not return the belt and he decided to wear it. SpongeBob went back to the kitchen and wonders what does the M button do.
SpongeBob pushed the button and the pickles shrunken. SpongeBob had an idea and shrunk the whole kitchen. Squidward then saw the kitchen shrunk and spots the belt. He then ask SpongeBob what is that and Squidward found out it was Mermaid Man's belt. Squidward then quotes: I can't believe he lend it to you. SpongeBob said he could not believe it either. Squidward then accuse SpongeBob he stole the belt. Squidward tells SpongeBob he will call Mermaid Man about the belt. SpongeBob was scared and does not want him to find out. SpongeBob shrunk Squidward. Squidward was then very angry and told SpongeBob to unshrink him. SpongeBob unfortunately cannot unshrink him. SpongeBob then asked Patrick for help. Patrick answered SpongeBob and said the belt is set to M for mini while it should be set to W for "wumbo". SpongeBob says wumbo is not a real word. Patrick then said wumbo is first grade and said more stuff about wumbo like wumbology (study of wumbo). SpongeBob then set it into W then he accidentally shrunk Patrick too. SpongeBob then put then in a jar to keep them safe. People then greets SpongeBob and SpongeBob shrunk every people who greets him. SpongeBob then shrunk everybody in Bikini Bottom including Mermaid Man and Barnacle Boy. The people asked how to unshrink them. Mermaid Man answered SpongeBob if he set is to wumbo. Everybody got mad at him and got inside of SpongeBob. They are destroying the insides of SpongeBob. Everybody then shouted: "Everything is too big!". SpongeBob got an idea and shrank Bikini Bottom and then he shrunk himself. Everything is now back to normal then Plankton came and he is now bigger than the city of Bikini Bottom.
- Patrick turns the "M" on Mermaid Man's Belt upside down to "W" to set it to "Wumbo" to re-size Squidward. A few moments later in the same scene, it is an "M" again, without him ever touching it.
- The Invisible Boat Mobile's color is pink Cadillac when visible. However, when SpongeBob and Patrick paint half of the boat mobile, or when they run it into a streetlight, it appears to be shaped like a boat.
- When SpongeBob shrinks himself, Mermaid Man's belt disappears.
- Mermaid Man's belt differs in color from other episodes.
- When the citizens of Bikini Bottom attack SpongeBob in this episode, he had a backbone but SpongeBob is an invertebrate as admitted in the episode Squirrel Jokes.
- This marks the only time that Mrs. SquarePants is seen without her husband Mr. SquarePants.
Episode Transcript: Mermaid Man and Barnacle Boy IV