The Bully / Just One Bite - S2-E17
Continuity mistake: In "Just One Bite," when everyone says "The only people who don't like Krabby Patties have never tasted one," the kitchen doesn't have a back door. After Squidward says "I gotta have more," he looks in from the back door.
The Bully / Just One Bite - S2-E17
Continuity mistake: In "The Bully" SpongeBob accidentally runs into Flats' dad's car and there is only one seat. Later Flats is shown sitting in the car.
The Bully / Just One Bite - S2-E17
Continuity mistake: When Flats moves out of the way we can see his pictures on the blackboard. The camera cuts away from him and back. The pictures are then taking up much more of the board than before (they go over the top of his head).
The Bully / Just One Bite - S2-E17
Continuity mistake: In one bit, Spongebob handcuffs himself to Squidward. When Squidward takes the Krabby Patty, the handcuffs are gone.
The Bully / Just One Bite - S2-E17
Continuity mistake: Just One Bite: After Squidward buries the Krabby Patty and tells SpongeBob that he hates it, when SpongeBob walks to the back door of the restaurant there's a window to the right of the door, but when Squidward makes plans to sneak a Krabby Patty that window has vanished.
The Bully / Just One Bite - S2-E17
Continuity mistake: The Bully: When Mrs. Puff enters the classroom and apologizes for being late, the door knob is at the left side of the door, but in following shots it's at the right side of the door.
The Bully / Just One Bite - S2-E17
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.
Answer: I believe this is the Season 6 episode "Spongicus".