Squidtastic Voyage/That's No Lady - S4-E15
Continuity mistake: In 'Squidtastic Voyage", Spongebob uses a remote to open the doors of the submarine. This remote disappears in the next shot.
Krabby Land / The Camping Episode - S3-E19
Continuity mistake: In "Krabby Land", Mr. Krabs is in his boat with Spongebob in front of the playground filled with children. After looking through a pair of binoculars, he drops them in front of the boat. However, in the next shot the binoculars are gone.
Mermaid Man and Barnacle Boy IV / Doing Time - S3-E1
Continuity mistake: In "Doing Time", Spongebob's entire face fills the chili bucket, but when he peeks out, his body is relatively smaller than the bucket.
Continuity mistake: In the episode "The Sewers of Bikini Bottom", Mr. Krabs is talking to the owners of the Krusty Krab Stadium and there are two pennants on the wall behind them. In a later shot through a window, there is only one pennant on the wall.
Continuity mistake: In "Patrick! The Game", the whole group is outside and Squidward rolls a die. The die disappears in the next shot.
Continuity mistake: In the episode "Patrick! The Game", Patrick puts on a surgeon mask. This mask eventually disappears in a later shot.
Continuity mistake: In "Patrick! The Game", Spongebob takes the rulebook and puts it off to the side. In the next shot, the book disappears.
Mermaidman Begins/Plankton's Good Eye - S8-E22
Continuity mistake: In "Mermaidman Begins", Mermaidman and Barnacleboy are running across a dock, about to jump into the sea. Next to them, on the right, there is a pelican sitting on a pillar. In the next shot at a different angle, the pelican is gone.
Mermaidman Begins/Plankton's Good Eye - S8-E22
Continuity mistake: In "Mermaidman Begins", the first time it shows Ernie microwaving the popcorn, there are 21 buttons on the microwave. In a later shot, there are now 24.
Mermaidman Begins/Plankton's Good Eye - S8-E22
Continuity mistake: In "Mermaidman Begins", the scientist experimenting on the ants knocks over the jar containing five ants. In the next shot, there are eight ants on the floor.
Mermaidman Begins/Plankton's Good Eye - S8-E22
Continuity mistake: In "Mermaidman Begins", the camera goes up one story to show a scientist. On the poster next to him, it shows various molecules and particles. In the next shot, the word "science" appears on the poster.
Karate Star - S8-E2
Continuity mistake: Spongebob is mopping the floor when a customer walks in the tell him about Patrick chopping everything. Two shots later, the mop and the water on the floor disappear.
Continuity mistake: Spongebob is looking up at the roots that are bouncing above him. In the first shot, there are only three above him. In the next shot, it shows more roots, with Spongebob standing under four.
A Flea in Her Dome / The Donut of Shame / The Krusty Plate - S5-E11
Continuity mistake: In "The Krusty Plate", Spongebob finds that one plate has a brown smudge on it. After an attempt to clean the plate, he lifts it up and the smudge is now a light shade of green.
Giant Squidward/No Nose Knows - S6-E7
Continuity mistake: In "Giant Squidward", Squidward goes to spray his wilting kelp with fertilizer and sets down a watering can right next to him. When the kelp goes back to normal in the next shot, the watering can disappears and is not seen again.
Hall Monitor / Jellyfish Jam - S1-E7
Continuity mistake: In "Hall Monitor" when SpongeBob is pretending to be the "open window bandit," you can see a red piece of coral outside of the house that he is about to break in to. When he jumps through the open window, frightens the people inside, and they run out of the house, the red piece of coral is gone.
Jellyfishing / Plankton! - S1-E3
Continuity mistake: In "Jellyfishing" when Squidward comes home in the bed thingy, the king jellyfish hovers above him. At first, Squidward is facing his house. But in the next shot, he is facing the road. When he replies "Ow" he is facing his house again.
Krab Borg / Rock-a-Bye Bivalve - S3-E8
Continuity mistake: The scene in episode Rock-a-Bye Bivalve where SpongeBob and Patrick start arguing about working for Junior at Patrick's house, SpongeBob is not inside the house. While SpongeBob is staring down at Patrick, his head is sticking out of the top of the hole in the ground. Once SpongeBob jumps in the top of the hole is way past their head.
Giant Squidward/No Nose Knows - S6-E7
Continuity mistake: In "No Nose Knows", Patrick is trying out his new nose. He passes through a cloud of perfume sprayed by a fish in front of the perfume shop. In the next shot, the fish and the perfume shop are gone.
Gullible Pants/Overbooked - S6-E19
Continuity mistake: In "Gullible Pants" when Mr. Krabs is about to exit the Krusty Krab, he looks at his watch, which disappears in the next shot.
Answer: I believe this is the Season 6 episode "Spongicus".