Naughty Nautical Neighbors / Boating School - S1-E4
Continuity mistake: The track changes between days.
Naughty Nautical Neighbors / Boating School - S1-E4
Continuity mistake: When Patrick runs out of Spongebob's house after Spongebob cries and says he's cheating, the lower right window beside the door is gone.
Naughty Nautical Neighbors / Boating School - S1-E4
Continuity mistake: When Squidward starts making pink bubbles with messages, he goes to his backyard. Notice he never closed the back window of his house. When he starts laughing because of the messages, suddenly the window is closed. After Patrick saves Squidward, the window is still closed, but when they go to the front of his house, the window is open.
Naughty Nautical Neighbors / Boating School - S1-E4
Continuity mistake: Boating School: When SpongeBob remembers that it's the day of the boating exam, the calendar reads "boating exam today," but then it reads "driving exam today."
Pizza Delivery / Home Sweet Pineapple - S1-E5
Continuity mistake: After Spongebob's house is gone, Squidward boo-hoos and goes into his house, then sounds happy. He starts throwing streamers and confetti out of his NOT-OPEN porthole. If the porthole was closed, they wouldn't fly out. Similar to some other ones in this show, and one in Fairly Odd Parents.
Pizza Delivery / Home Sweet Pineapple - S1-E5
Continuity mistake: In "Home Sweet Pineapple", Spongebob goes into Squidward's house to spend the night and sits in his bed with the pillow just the right size for him. But in the next shot, when Squidward climbs into bed next to him, the pillow has drastically grown and now both of them can lay on it perfectly.
Pizza Delivery / Home Sweet Pineapple - S1-E5
Continuity mistake: In "Pizza Delivery", Spongebob points out the antennae for the boat during his vehicle inspection, but in a few shots, when he's checking the tire pressure, the antennae has vanished.
Mermaid Man and Barnacle Boy / Pickles - S1-E6
Continuity mistake: At the beginning of "Mermaid Man and Barnacle Boy", when SpongeBob and Patrick are watching TV viewing Mermaid Man and Barnacle Boy show, you can see that these heroes have 5 fingers on their hands, as the real human beings. However, when SpongeBob and Patrick meet these heroes, as in the rest of the show, you can see that now, the heroes, have 4 fingers on their hands, as cartoon characters usually have.
Mermaid Man and Barnacle Boy / Pickles - S1-E6
Continuity mistake: In the episode "Pickles", there is a large fish named Bubble Bass. Although his name is Bubble Bass, the captions say his name is Bubble Bath. It is clear that Spongebob is saying "Bass" not "Bath", and his name is given as Bubble Bass in SpongeBob's Diner Dash.
Mermaid Man and Barnacle Boy / Pickles - S1-E6
Continuity mistake: Mermaid Man and Barnacle Boy: Mermaid Man wears green tights, but after SpongeBob absorbs the water ball like "some kind of evil sponge," when Mermaid Man and Barnacle Boy start doing the dog paddle, Mermaid Man's tights have vanished in this shot.
Mermaid Man and Barnacle Boy / Pickles - S1-E6
Continuity mistake: Mermaid Man and Barnacle Boy: When Barnacle Boy opens the box with the two rings inside, in the closeup the "B" ring is on the left and the "M" ring on the right, but in the wideshot Barnacle Boy removes the ring on the left (the "B") and places it on Mermaid Man's finger, then in the next shot we see it's the "M" ring, before both rings vanish.
Mermaid Man and Barnacle Boy / Pickles - S1-E6
Continuity mistake: Mermaid Man and Barnacle Boy: When SpongeBob and Patrick (dressed in their superhero costumes) exit the pineapple the front door opens at the right side (outward), but after getting on Squidward's nerves, when they retreat back inside the front door opens the opposite way at the left side (inward).
Hall Monitor / Jellyfish Jam - S1-E7
Continuity mistake: Hall Monitor: When SpongeBob sees the open window to the house, the window is opened to the left. When the two fish run out of the house after SpongeBob scares them, the window is opened the opposite way, then reverts back in the next shot. (00:05:19)
Hall Monitor / Jellyfish Jam - S1-E7
Continuity mistake: When SpongeBob asks Squidward to play his clarinet better, he is wearing his night shirt which is purple, but in the next shot he is wearing his normal shirt which is brown.
Hall Monitor / Jellyfish Jam - S1-E7
Continuity mistake: In "Jellyfish jam", when SpongeBob shows the jellyfish to Squidward, and the jellyfish starts to do a lot of things, you see that Squidward is looking by his porthole in his house. The porthole is closed. However, when he says "How can anybody have fun with a jellyfish?" his arms go outside the porthole. But this is impossible, since the porthole is closed.
Hall Monitor / Jellyfish Jam - S1-E7
Continuity mistake: In episode 1-7, Hall Monitor, Patrick says Spongebob is at the intersection of Conch and Coral, and we then see the street sign. However when we see Spongebob standing on the road, there is only one road, and no intersection.
Hall Monitor / Jellyfish Jam - S1-E7
Continuity mistake: Hall Monitor: After SpongeBob walks out of class the bell rings and he gets trampled, and when Mrs. Puff follows him outside the classroom door is wide open, but then the entire door suddenly vanishes.
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.
Sandy's Rocket / Squeaky Boots - S1-E8
Continuity mistake: When SpongeBob is explaining why he thinks there are aliens in Sandy's Rocket, you can see a plant and rocks. We see a wide shot and it has now disappeared. (00:02:00)
Sandy's Rocket / Squeaky Boots - S1-E8
Continuity mistake: In "Squeaky Boots", Mr. Krabs starts hearing squeaky sounds everywhere. Then he goes mad and says he took the boots from SpongeBob. At this point, notice the restaurant floor's colour. Mr. Krabs lifts the whole restaurant, but we can still see some floor (where Krabs is). Notice that now the colour of the floor has changed.
Answer: I believe this is the Season 6 episode "Spongicus".