SpongeBob's House Party (aka Party Pooper Pants) - S3-E10
Continuity mistake: When Spongebob comes home after being arrested, he picks a spare key up from under his mat and gets angry at himself for trying to break in the night before. When he walks in, discomfort on his face, the mat is gone.
Dying For Pie / Imitation Krabs - S2-E6
Continuity mistake: Before Spongebob drops the pie in Squidward's face, the rock he tripped on was never there.
Something Smells / Bossy Boots - S2-E1
Continuity mistake: In Something Smells, when Spongebob is making the sundae, the peanut plant vase that he throws in changes direction between shots.
The Great Snail Race / Mid-Life Crustacean - S3-E15
Continuity mistake: When Gary was spinning out of control, there were at least 5 lanes on the track but before there were only 3.
You Wish ('Shanghaied') / Gary Takes A Bath - S2-E11
Continuity mistake: When Gary almost goes into the mud and his head is hovering over it, in the far shot, he is just sitting there.
Survival of the Idiots / Dumped - S2-E8
Continuity mistake: In Dumped, when Patrick is finished brushing his teeth, his toothbrush disappears.
Jellyfishing / Plankton! - S1-E3
Continuity mistake: The words "Total Control" constantly appear and disappear from the controlling device in Spongebob's brain.
Something Smells / Bossy Boots - S2-E1
Continuity mistake: When Spongebob jumps on a car and asks "am I ugly", and the guy blows up his car, you see his car has small little wheels. When one of the wheels bounces on Spongebob, it is huge.
Fools in April / Neptune's Spatula - S1-E19
Continuity mistake: When Spongebob grabs Squidward's legs you only see him grabbing at two of Squidward's legs and the other two legs have disappeared, but when the shot changes they're back again.
No Weenies Allowed / Squilliam Returns - S3-E6
Continuity mistake: When Squidward has sort of a strict conversation with Spongebob, Mr. Krabs, and later Patrick, the 3 of them he was talking to, were side by side, but a shot later, Mr. Krabs and Spongebob are side by side, but farther from Patrick.
The Sponge Who Could Fly (aka The Lost Episode) - S3-E16
Continuity mistake: After the walk cycles, the color bars change between shots.
Nasty Patty / The Idiot Box - S3-E4
Continuity mistake: In the scene where Spongebob and Mr. Krabs bury the health inspector, Spongebob buries him so that way his head is above ground covered by a pile of dirt. In the next shot of the buried health inspector, he is buried horizontally.
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.
Naughty Nautical Neighbors / Boating School - S1-E4
Continuity mistake: In 'Boating School' when Mrs. Puff blows up she has a deep voice, but in all the other episodes her voice stays the same.
Something Smells / Bossy Boots - S2-E1
Continuity mistake: In Something Smells, when Spongebob finishes eating the sundae and he comes out of the room and drops his spoon. He turns to his right, the spoon that he dropped has disappeared.
Mermaid Man and Barnacle Boy IV / Doing Time - S3-E1
Continuity mistake: In the scene where the guard pulls Mrs. Puff out of the rock yard, her hat is red, then blue, then red again throughout the cuts in the scene.
The Snowball Effect / One Krabs Trash - S3-E3
Continuity mistake: In One Krabs Trash, Spongebob pays Mr. Krabs with what looks like two dollars, which should have been five, and when he comes back he has two dollars that doubles into four in the next shot of him leaving.
Continuity mistake: Sleepy Time: When everyone woke up SpongeBob near the end, Pearl is seen without her ponytail, but in the next shot, she has a nightcap on.
Fools in April / Neptune's Spatula - S1-E19
Continuity mistake: In "Neptune's Spatula", Patrick takes a picture of SpongeBob holding the spatula. When this happens, we can see that SpongeBob is a little worried because clouds have appeared there. However, after a while, Patrick shows the picture to Neptune, and we can see that in the picture SpongeBob is smiling and pointing with the spatula.
Something Smells / Bossy Boots - S2-E1
Continuity mistake: In Something Smells, once Spongebob finishes saying hello to all the band people, he says "Is it something I said?". You see him start to walk back but when you see a close up of him, a fire hydrant appears.
Answer: I believe this is the Season 6 episode "Spongicus".