The Fish Bowl/Married to Money - S9-E18
Continuity mistake: In "The Fish Bowl", Sandy has a wristwatch on her right wrist when she first appears on the bus. When she sits near the front to observe the fish, the wristwatch has disappeared and doesn't reappear.
The Fish Bowl/Married to Money - S9-E18
Audio problem: In "The Fish Bowl", after Patrick takes the bowls of ice cream and eats them both, he throws them behind him. The bowls just disappear in mid air without leaving the frame (also an "other mistake") but the sound of the ceramic bowls breaking is still heard.
The Fish Bowl/Married to Money - S9-E18
Continuity mistake: In "Married to Money", Pearl cries and her tears flood Mr. Krabs' house. When this happens, he pulls a in the floor to let the water drain. In a few shots, this plug and drain are missing.
Answer: I believe this is the Season 6 episode "Spongicus".