Continuity mistake: When Patchy lifts his eye patch to rub his eye and puts the patch on his right eye. In the next shot the patch is on his left eye.
Continuity mistake: Gary leaves big saliva trails. When Squidward realizes that Gary leaves these saliva trails, we can see that is a trail in front of Squidward's house. When Squidward tells SpongeBob about these trails in the language of the past, we can see that the trail of the saliva has changed: it bigger and almost in all the scenery. After a while, we see that the road goes directly to Squidward's house, to its door. How did the road change, if we haven't seen Gary moving?
Character mistake: In the credits, when Jonathan Silsby is credited as the puppeteer, "puppeteer" is misspelled as "pupeteer." (00:22:34)
Continuity mistake: When Squog runs to his house with the fire, he tries to open his door, but that door never existed previously in the episode. (00:17:55)
Other mistake: When the credits say that the live-action island footage is by Bad Clams Productions, Inc, there is a missing space between the words "footage" and "by." (00:22:55)
Other mistake: In the credits, Tom Kenny, Bill Fagerbakke, and Rodger Bumpass are credited for playing SpongeBob, Patrick, and Squidward. However, Patrick and Squidward's names should be "Patar" and "Squog," and "SpongeGar" should be shown along with SpongeBob's name (SpongeBob makes a small appearance near the start of the episode). (00:22:32)
Character mistake: Near the end of the second Patchy the Pirate segment, the narrator says, "What will SpongeBob do with fire?" However, the character's name is actually "SpongeGar." (00:14:29)
Continuity mistake: When Patar heats the squished crab in the fire, it's in his left hand. But in the next shot when he eats it, it's in his right.
Answer: I believe this is the Season 6 episode "Spongicus".