Enemy In-Law/Mermaidman and Barnacleboy VI: The Motion Picture - S4-E7
Continuity mistake: Patrick turned out to have put the lens cap on the camera before they started to film. But when the first scene was being filmed, there was no sign of the lens cap on the camera. There was also no sign of the lens cap on the camera when the Pearl "Boatmobile" fell off the cliff.
Enemy In-Law/Mermaidman and Barnacleboy VI: The Motion Picture - S4-E7
Other mistake: Plankton's phone doesn't have a 0 button on it.
Answer: I believe this is the Season 6 episode "Spongicus".