Your Shoe's Untied / Squid's Day Off - S2-E2
Continuity mistake: When SpongeBob is sad because he can't tie his shoes, you see is night. When Gary ties his shoes, suddenly it becomes day.
Your Shoe's Untied / Squid's Day Off - S2-E2
Continuity mistake: In "Squid's Day Off", sometimes Squidward's house door opens to the left, and sometimes opens to the right.
Your Shoe's Untied / Squid's Day Off - S2-E2
Continuity mistake: In Your Shoe's Untied, when Spongebob takes the patty to Squidward, it's just a patty with lettuce, but in one shot, you can see cheese and pickles on it.
Your Shoe's Untied / Squid's Day Off - S2-E2
Continuity mistake: In Squid's Day Off, when all of the coins go out of the cash register, you see 14 coins drop. When Squidward picks up the coins, there are only 12.
Your Shoe's Untied / Squid's Day Off - S2-E2
Continuity mistake: In "Squid's Day Off" Squidward gets mad at Spongebob for ringing a bell over and over again. It shows the bell in the window to the left. Later, when it shows Squidward throwing the cash register onto the ordering desk, the bell is gone from the window. In the next shot of Spongebob, the bell is back in the window. Then, when Squidward shouts "No." the bell is gone again.
Your Shoe's Untied / Squid's Day Off - S2-E2
Continuity mistake: In "Your Shoes Untied", when he is in the Krusty Krab kitchen. In between shots when Squidward keeps asking Spongebob to give him the Krabby Patty, the patties on the grill disappear and reappear between shots.
Your Shoe's Untied / Squid's Day Off - S2-E2
Continuity mistake: At the beginning of "Squid's Day Off", There is a tiny bell painted gold sitting on the opening between the kitchen and restaurant. When the shot changes, the bell disappears, then reappears when the shot changes again.
Big Pink Loser / Bubble Buddy - S2-E3
Continuity mistake: Bubble Buddy: When Spongebob brings his Bubble Buddy to the Krusty Krab, Squidward's restaurant hat is visible on his head. It is not seen when he looks into Bubble Buddy when he says, "That Bubble Buddy sure looks good."
Big Pink Loser / Bubble Buddy - S2-E3
Continuity mistake: It seems to me that half the cards that Spongebob used for the card snail have disappeared when Patrick comes in.
Big Pink Loser / Bubble Buddy - S2-E3
Continuity mistake: When Patrick in Spongebob clothing is first revealed (when the rock is raised), Patrick has no collar, yet in other shots the shirt has a collar.
Big Pink Loser / Bubble Buddy - S2-E3
Continuity mistake: At the beginning of "Big Pink Loser", Patrick's rock is brown. When Spongebob and Patrick run with each other, out of the Krusty Krab, Spongebob runs into Patrick's rock, painted like Spongebob's pineapple house, yet when Patrick said "I'm going to defend my title" or something like that, the rock is brown. The rock can't possibly paint itself.
Big Pink Loser / Bubble Buddy - S2-E3
Continuity mistake: The broom that Patrick throws on the ground in Big Pink Loser disappears soon after.
Mermaid Man and Barnacle Boy III / Squirrel Jokes - S2-E4
Continuity mistake: In "Squirrel Jokes", on Spongebob's second act when Sandy laughs about the bronze fish, she is between 2 people. When you see her again she isn't between anybody.
Mermaid Man and Barnacle Boy III / Squirrel Jokes - S2-E4
Continuity mistake: In Squirrel Jokes, when Spongebob comes out for his second act, there's a back shot of a crowd, and there is one guy in the front right (from the back view) who is green. There is another front shot of the crowd and the guy completely disappears.
Mermaid Man and Barnacle Boy III / Squirrel Jokes - S2-E4
Continuity mistake: In "Squirrel Jokes", SpongeBob wants to make a joke about a fork. Someone screams "Forks?" and SpongeBob becomes more nervous. After that, the fork disappears from where it was.
Mermaid Man and Barnacle Boy III / Squirrel Jokes - S2-E4
Continuity mistake: In "Squirrel Jokes", right when he comes out of the curtains people put their hands up, but in a front view their hands are down.
Mermaid Man and Barnacle Boy III / Squirrel Jokes - S2-E4
Continuity mistake: In "Squirrel Jokes", when Spongebob tells the joke about Squirrel in the second act she's at a table alone, but in the next wider shot there's a chair next to her.
Mermaid Man and Barnacle Boy III / Squirrel Jokes - S2-E4
Continuity mistake: In "Squirrel Jokes", at the beginning of Spongebob's 2nd act when he's at his mirror backstage, a random object appears on the table.
Mermaid Man and Barnacle Boy III / Squirrel Jokes - S2-E4
Continuity mistake: In Squirrel Jokes, when Spongebob gives Sandy the flowers, the number of the flowers varies from 6 to 8 in different shots.
Mermaid Man and Barnacle Boy III / Squirrel Jokes - S2-E4
Continuity mistake: During Spongebob's act, he says to the audience, ".I'd like to give a special thanks to my friend Sandy over here" and the spotlight moves from Spongebob to Sandy. A few shots later, when Spongebob is talking to Sandy, the spotlight is suddenly no longer on Sandy. Then when Spongebob yells "Am I right?" to the audience, the spotlight is on him and as he turns to talk to Sandy again, the spotlight is altogether gone; it's not on either one of them.
Answer: I believe this is the Season 6 episode "Spongicus".