The Chaperone / Employee of the Month - S1-E12
Continuity mistake: Spongebob says that this is the 27th award he has won, yet when he is standing in front of the pictures there are at least 30.
The Chaperone / Employee of the Month - S1-E12
Continuity mistake: Spongebob absorbs the pink punch making him look pink in 2 shots - one showing him squirting punch out of his nose, but a shot after that shows him yellow.
Scaredy Pants / I Was a Teen-age Gary - S1-E13
Continuity mistake: When Spongebob is cutting his Jack-O-Lantern, he cuts out an eye on his right, but in the shot from inside the pumpkin the eye hole is gone, then the eye reappears.
Scaredy Pants / I Was a Teen-age Gary - S1-E13
Continuity mistake: Spongebob's belt is missing when his clothes are first revealed while dangling in midair.
Scaredy Pants / I Was a Teen-age Gary - S1-E13
Continuity mistake: The Krusty Krab is filled with Halloween decorations during the episode, but when Spongebob jumps to hide in a barrel there are no decorations in sight.
Scaredy Pants / I Was a Teen-age Gary - S1-E13
Continuity mistake: When Spongebob agrees to hear Mr. Krabs' story, their seats come out of nowhere.
SB-129 / Karate Choppers - S1-E14
Continuity mistake: When Spongebob throws the Krabby Patties on Squidward's head there are only 6 of them, later there's at least 8.
SB-129 / Karate Choppers - S1-E14
Continuity mistake: When Squidward is in the white place and crashes through the floor, he doesn't have his clarinet before he crashes through the floor. But when he is in the time machine, he has his clarinet.
SB-129 / Karate Choppers - S1-E14
Continuity mistake: SB-129: When Squidward opens the door to the time machine, the exterior side of the door has a handle at the left side and opens at the left, but the interior side of that door also has the handle at the left side, though it should be at the right side. Then when Squidward activates the machine, the exterior handle is now at the right side and it opens at the right.
SB-129 / Karate Choppers - S1-E14
Continuity mistake: In "SB-129", every time Squidward goes to answer the door to find Spongebob and Patrick there, the picture on the wall next to the door changes noticeably.
SB-129 / Karate Choppers - S1-E14
Continuity mistake: In "Karate Choppers" when SpongeBob sticks his arm through Sandy's phone, Sandy sticks SpongeBob's hand through the other end, then Sandy puts the phone down and SpongeBob's hand immediately disappears.
Continuity mistake: When all of Spongebob's friends are formed around him, there's one scene where Pearl's hat disappears and then reappears, so for a few seconds she's completely bald. Her hair isn't even there.
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.
Continuity mistake: In "Suds" after Spongebob crashes through his bedroom window, the blanket is hanging over the side and is all wavy, but when he's in bed it's completely plain and doesn't hang over the sides.
Continuity mistake: In "Sleepy Time" when the neighbours are crowded around Spongebob, Plankton is standing on the end of the bed. When the angle changes, he's gone. Then he jumps onto the bed before Patrick joins them.
Continuity mistake: In "Sleepy Time", Spongebob is driving a car in his dream. When he starts to drive faster, he sticks his tongue out on his left cheek. When he makes a left turn in the next shot, it's sticking out on the right cheek.
Valentine's Day / The Paper - S1-E16
Continuity mistake: In "Valentine's Day", Patrick starts searching his present in the fair. Then he goes to a mountain and falls thinking that there will be his present. This mountain wasn't there before, even when they arrived to the fair.
Valentine's Day / The Paper - S1-E16
Continuity mistake: In Valentine's Day, almost at the end, Patrick smashes some presents with his foot. After a while, Sandy arrives with Patrick's present (a chocolate globe), and you can see that the presents have dissapeared.
Valentine's Day / The Paper - S1-E16
Continuity mistake: In "Valentine's Day", SpongeBob and Patrick arrive at the fair. They watch the fair. Patrick says "You bought me a fair?", and Patrick runs to the fair. When he starts saying, "Get out of my fair.", we see that SpongeBob is closer to the fair than he was before.
Valentine's Day / The Paper - S1-E16
Continuity mistake: The Paper: The front door of Squidward's house repeatedly switches between opening at the right side and opening at the left side, and the round door knob also changes to a door handle as well, but then reverts back to the round knob.
Answer: I believe this is the Season 6 episode "Spongicus".