Continuity mistake: When Pearl gives SpongeBob the new costume for the Krusty Krab, she gives SpongeBob a mirror. In the mirror, Squidward appears and tells him not to accept the costume. If you notice, Squidward is at the LEFT of SpongeBob. Because is a mirror, in the real life he would be at the RIGHT of SpongeBob. When a shot is shown of SpongeBob and Squidward, you can see that Squidward isn't at the RIGHT of SpongeBob, he's at the LEFT.
Continuity mistake: In the episode "The Bully," when Flats punches Spongebob, Spongebob states to Gary that he's made out of some spongy material, that it absorbs his blows and it doesn't hurt him at all. But in later episodes, when Spongebob gets knocked out that never happens anymore.
Character mistake: In the beginning of "One Krabs Trash" Spongebob only has one bill in his hand, a 5 dollar bill. When he goes to his house and comes back, he says he found 68 cents. Therefore, he has 5 dollars and 68 cents. However, he has two dollar bills and a few pennies in his hand, which cannot be made into $5.68.
Revealing mistake: In "Spongebob Meets The Strangler" when that fish holds up Spongebob's dry cleaning at the supermarket, it looks like he is holding it up with a coathanger because his hand is up in the air, but you can easily see nothing is holding it up. It's just floating up in the air.
Continuity mistake: When Patrick is dressed as food for the "monster" in "Wormy," when the butterfly is on P,atrick's butt he spits out the apple in his mouth and it floats to the top of the water helmet. But when the butterfly is on his helmet, the apple is gone.