Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Revealing mistake: In one scene with Spongebob, Patrick, an old lady, and her almost dead mom, in one part Spongebob has no holes on his face. There is also a light-colored spot near Patrick's mouth.
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Continuity mistake: When SpongeBob and Patrick are pretending that they need an operation and that fish falls down the stairs, if you look at Patrick's head he has no bandage on his head. But when he looks at SpongeBob right after that fish falls down the stairs, a bandage suddenly appears on his head.
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Continuity mistake: The second time the chocolate guy chases Spongebob and Patrick, they run away and leave all their bags. But, in the next shot, they have their bags with them.
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Continuity mistake: When Barnacle Boy and E.V.I.L. are hiding behind the rock you can see Barnacle Boy's fingers. In the next shot he is wearing gloves.
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Character mistake: Chocolate With Nuts: When Spongebob and Patrick go to the first house, Spongebob tells the man, "Good afternoon, sir." When they go to the second house, he says, "Good morning, sir." (00:02:52)
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Continuity mistake: Chocolate With Nuts: While SpongeBob and Patrick are selling chocolate, the elderly female's door opens at the left, but after Patrick claims their chocolate will make you live forever, the door is open the opposite way.
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Continuity mistake: Mermaid Man And Barnacle Boy V: When Barnacle Boy shouts that he wants to be called Barnacle Man and demands respect, the door to Krabs' office is missing. Then it happens again when the news comes on.
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Continuity mistake: In 'Chocolate With Nuts' the bandaged up fish's house's front stairs had only a few steps when Spongebob and Patrick approached, but as the fish falls down there's suddenly a lot more.
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Continuity mistake: In "Chocolate With Nuts", Patrick and Spongebob buy the chocolate holding bags from one man, they walk to the next house next door. When they are standing next to the door, the first house behind them disappears.
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Continuity mistake: After MermaidMan screams "To Make Out Reef" he accidentally falls over on his chair. When Patrick complains that they aren't gonna get pizza the chair is back up again.
Answer: I believe this is the Season 6 episode "Spongicus".