Continuity mistake: When Spongebob is outside, and he takes out his "to do list" at first he is holding it with his right hand, but when it shows the front of the paper, you see that it is his left hand. Then it is his right hand again.
Revealing mistake: In one scene with Spongebob, Patrick, an old lady, and her almost dead mom, in one part Spongebob has no holes on his face.
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: In "Valentine's Day", SpongeBob and Patrick arrive at the fair. They watch the fair. Patrick says "You bought me a fair?", and Patrick runs to the fair. When he starts saying, "Get out of my fair.", we see that SpongeBob is closer to the fair than he was before.
Continuity mistake: In "No Free Rides", when Spongebob and Mrs. Puff are fighting in the car, they eventually go over a cliff. We see a view of a police car under them, next to the cliff and a billboard. We also see a shot of the police car facing a hill or two. The car flies out of nowhere onto the police car, from behind a hill, not off the cliff. The landscape in the scene changes in each shot.