Bummer Vacation/Wigstruck - S4-E14
Continuity mistake: In Wig Struck, Patrick takes a bite out of Spongebob's wig and in the next shot, the wig is restored.
Bummer Vacation/Wigstruck - S4-E14
Deliberate mistake: When SpongeBob is playing with his Krusty Krab action figures, their faces change expressions instantly.
Suggested correction: This is simply one of the many gags that occur in this show. In the same scene, SpongeBob has a third arm while playing with the action figures. Problematic? No, that's a gag too. Throughout the show, the characters are capable of doing many impossible tasks (drinking water underwater, floating, growing limbs, etc.). The expressions on the action figures changing is another one of the impossible things that can happen in this fantasy world.

Bummer Vacation/Wigstruck - S4-E14
Other mistake: Bummer Vacation: When Spongebob says, "You're right, Gary. It is unhealthy to think of the Krusty Krab while I'm on vacation," his legs are missing. (00:05:55)