Chum Bucket Supreme/Single Cell Anniversary - S6-E22
Continuity mistake: In "Single Cell Anniversary", Spongebob places a megaphone on the ground. In a few shots, the megaphone has disappeared by itself.
Chum Bucket Supreme/Single Cell Anniversary - S6-E22
Continuity mistake: In "Chum Bucket Supreme", Patrick is painting the slogan "Krabby Patties Are Fum" on the Krusty Krab with no hole in the back of his head. In a few shots, Patrick is standing in the same spot, and the hole in his head has reappeared.
Chum Bucket Supreme/Single Cell Anniversary - S6-E22
Continuity mistake: In "Chum Bucket Supreme", Mr. Krabs hears the sound of Plankton's cash register, and the wide shot shows him standing on the pavement around the Krusty Krab. In the next shot, he is now standing in sand.
Chum Bucket Supreme/Single Cell Anniversary - S6-E22
Continuity mistake: In "Chum Bucket Supreme", Mr. Krabs notices that there are only two customers in the Krusty Krab. When he goes up to the front window, the customers and their tables have vanished.
Chum Bucket Supreme/Single Cell Anniversary - S6-E22
Continuity mistake: In "Chum Bucket Supreme", Plankton rips up a piece of paper on top of Karen. In a few shots, the ripped paper disappears.
Answer: I believe this is the Season 6 episode "Spongicus".