Help Wanted / Reef Blowers / Tea at the Treedome - S1-E2
Continuity mistake: In "Help Wanted", the last time SpongeBob says "I'm ready!", his collar turns red.
Revealing mistake: In "Patrick! The Game," when Squidward holds out the notepad, it's obviously written on. Just when the bubble transition comes, the notepad and all the other papers on the floor clear themselves.
Help Wanted / Reef Blowers / Tea at the Treedome - S1-E2
Revealing mistake: When Spongebob uses his binoculars, his teeth turn yellow for one frame.
Your Shoe's Untied / Squid's Day Off - S2-E2
Character mistake: In "Squid's Day Off", a wide shot shows Mr. Krabs exiting the hospital, except the building says" ENEREENCY" instead of "EMERGENCY."
Sandy, SpongeBob and the Worm / Squid on Strike - S2-E18
Other mistake: Squid on Strike: When Squidward looks at himself in his bathroom mirror, his buttons are on the left side of his pyjamas in the reflection. When he is shown in bed a few seconds later, the buttons are on the same side; the reflection was not reversed. (00:09:07)
The Bully / Just One Bite - S2-E17
Continuity mistake: Just One Bite: When Squidward opens the door to the Patty Vault, the door opens to the left side. In the next shot, the door is not visible anymore, and when we see it again two shots later, it is now opened to the right side. A wheel also appears on the interior side of the door, which wasn't there before. (00:09:10)
Character mistake: In the credits, when Jonathan Silsby is credited as the puppeteer, "puppeteer" is misspelled as "pupeteer." (00:22:34)
Continuity mistake: When Squog runs to his house with the fire, he tries to open his door, but that door never existed previously in the episode. (00:17:55)
Grandma's Kisses / Squidville - S2-E9
Other mistake: Grandma's Kisses: After Patrick sucks all of Grandma's cookies into his mouth like a vacuum, as the cookie rolls towards SpongeBob, his lower body is missing, then it appears once he moves. (00:07:44)
Grandma's Kisses / Squidville - S2-E9
Other mistake: Grandma's Kisses: After Patrick bites his finger while eating the cookie, his shorts are not fully coloured in at the bottom of the screen, but they instantly are once Grandma kisses his finger. (00:08:37)
Grandma's Kisses / Squidville - S2-E9
Other mistake: Grandma's Kisses: After Patrick sucks all of Grandma's cookies into his mouth like a vacuum, a cookie rolls towards SpongeBob, and as he says, "It appears to be my lunch hour," a watch appears on his left wrist mid-shot, then disappears. (00:07:49)
Grandma's Kisses / Squidville - S2-E9
Other mistake: Grandma's Kisses: When SpongeBob goes to his grandma's house with Patrick, Grandma tells him to give her a kiss, and in the next shot of SpongeBob, his right leg is missing. (00:05:13)
Other mistake: When the credits say that the live-action island footage is by Bad Clams Productions, Inc, there is a missing space between the words "footage" and "by." (00:22:55)
Krabby Land / The Camping Episode - S3-E19
Continuity mistake: Krabby Land: After Mr. Krabs speaks to the children as Krabby the Clown, he goes inside his office. Then, when SpongeBob starts talking to Mr. Krabs, the door to Mr. Krabs' office has vanished; then it reappears a moment later. (00:10:18)
No Weenies Allowed / Squilliam Returns - S3-E6
Other mistake: Squilliam Returns: After Squilliam tells Squidward that he is a cashier just like him, Mr. Krabs is shown playing his small violin, but his eyes are coloured white instead of their usual pale green colour. (00:23:07)
Dying For Pie / Imitation Krabs - S2-E6
Other mistake: Dying for Pie: When SpongeBob seems to have exploded behind the brick wall, a brick flies out of the wall. Then, when the second explosion happens, the brick reappears in the wall mid-shot, then disappears when the wall hits the floor. (00:10:20)
Dying For Pie / Imitation Krabs - S2-E6
Other mistake: Dying for Pie: Near the end, Squidward tells SpongeBob that he spent the whole day with him doing all kinds of ridiculous things because he was supposed to explode. Right when Squidward says, "explode," a small portion of his head gets cut off briefly. (00:10:52)
Welcome to the Chum Bucket / Frankendoodle - S3-E2
Continuity mistake: Frankendoodle: When DoodleBob first starts beating up Squidward, the door to Squidward's house is open, but two shots later, the door has completely vanished. (00:16:32)
Sandy, SpongeBob and the Worm / Squid on Strike - S2-E18
Continuity mistake: Sandy, SpongeBob, and the Worm: When SpongeBob makes a necklace out of the paper clip and string, he holds up the paper clip that he made into an "S" shape as he wears the necklace. In the next shot, the paper clip is facing the opposite way, then reverts back in the following shot. (00:22:20)
Survival of the Idiots / Dumped - S2-E8
Other mistake: Dumped: After Patrick starts playing tag with Gary and SpongeBob, Gary starts crawling around Patrick's body and does that up until it's dark out. SpongeBob is not wearing a watch on his left wrist, but then he looks at his watch, which suddenly appears on that wrist mid-shot. Then, right before he picks up Gary, the watch disappears. (00:14:06)
Answer: I believe this is the Season 6 episode "Spongicus".