The Chaperone / Employee of the Month - S1-E12
Continuity mistake: When Spongebob, in his black suit and long legs, is at the door of Mr Krabs', he used a lever to lower himself down. When we cut back to Spongebob, it's gone.
The Chaperone / Employee of the Month - S1-E12
Continuity mistake: When Spongebob is crying next to the employee of the month wall, (just before he says "How could I have let the quality of my work slip so much?") the order of the pictures is messed up. It goes December, February, January. Then, when we see the close-up of Squidward's face laughing, the order is correct again.
The Chaperone / Employee of the Month - S1-E12
Continuity mistake: In "Employee of the Month", when Spongebob is spying on Squidward, Squidward puts his alarm clock to the left of his bed. When Spongebob tries to get the clock, it is now to the right of Squidward's bed.
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: SB-129: After Squidward accidentally breaks the lever to the time machine, he holds the lever with two hands, but he holds it with only one hand in the next close-up shot. (00:09:54)
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.
Answer: I believe this is the Season 6 episode "Spongicus".