Continuity mistake: When Mr. Krabs and SpongeBob are standing in front of the bomb after it lands but doesn't go off, the clock inside Mr. Krabs' office can be seen from the kitchen. The time on the clock is 5:00, but in the next shot, the time on the clock is suddenly 3:00. The bomb is then revealed to be a mechanical hand, and the time on the clock is now 5:00 again.
Continuity mistake: When SpongeBob accidentally reveals the location of the formula, Plankton drops the feather he is holding and lands in front of him. The feather remains on the floor, but when Pearl walks into the kitchen, the feather has suddenly vanished, and reappears in front of Plankton in the next shot.
Continuity mistake: When Plankton is telling Karen, "There's a whale in the laboratory," he is jumping up and down with his arms in the air, but in the next shot, his arms are suddenly down at his side.
Continuity mistake: Plankton is questioning Mr. Krabs and SpongeBob for the formula whilst they are stuck inside a mechanical hand. The area where the screw is located can be seen on both sections of the hand, on the right and left hand side. In some shots the right side of the hand completely obscures the screw on the left side, and in some shots not. Also, in one shot, the screw changes colour and becomes white.
Continuity mistake: After Plankton blows up the Krusty Krab roof, Mr. Krabs enters the kitchen through the door leading from his office. When he opens the door, it falls off and leans against the counter beside the door. When SpongeBob approaches Mr. Krabs, the door is suddenly lying on the floor.
Continuity mistake: When Mr. Krabs walks into the kitchen after Plankton detonates the roof, the door falls off and there is no hinge attached to the door, but once Plankton has flown in through the hole in the roof, a hinge has suddenly appeared on the door.
Spongebob's Last Stand - S7-E22
Continuity mistake: As soon as a man stamps on a tambourine, it disappears 2 shots later.
Enchanted Tiki Dreams - S7-E23
Continuity mistake: Spongebob goes to set a canvas on the ground. On the spot where he is putting the canvas down, there are three flowers on the ground. In the next shot, after he set the canvas down, the flowers have disappeared.
Continuity mistake: Spongebob is looking up at the roots that are bouncing above him. In the first shot, there are only three above him. In the next shot, it shows more roots, with Spongebob standing under four.
Karate Star - S8-E2
Continuity mistake: Spongebob is mopping the floor when a customer walks in the tell him about Patrick chopping everything. Two shots later, the mop and the water on the floor disappear.
Buried in Time/Shellback Shenanigans - S8-E5
Continuity mistake: The authentic plate that SpongeBob accidentally drops in the time capsule and breaks repairs itself when it is seen inside the capsule after being buried.
Tunnel of Glove/Love That Squid - S8-E14
Continuity mistake: In "Tunnel Of Glove" the amount of police tape on the entrance of the tunnel of glove changes. Some shots there are three pieces of tape, others there are four.
The Krabby Patty That Ate Bikini Bottom/Bubble Buddy Returns - S8-E15
Continuity mistake: At the beginning of Bubble Buddy Returns, right after SpongeBob reads the letter from Bubble Buddy, Gary's swirl is blue and his spots are red.
The Krabby Patty That Ate Bikini Bottom/Bubble Buddy Returns - S8-E15
Continuity mistake: The giant Krabby Patty eats SpongeBob's shoe and sock in the kitchen. But by the time SpongeBob and Squidward run to the door and are stopped by Mr. Krabs, the shoe and sock have magically reappeared.
Squidward's School for Grown Ups - S8-E18
Continuity mistake: Spongebob uses a razor to try and shave off Patrick's beard, which falls onto the ground. In two shots, the razor disappears.
Continuity mistake: When we see the "Flabby Patty" for the first time, there are 8 fish in line. When we see it the second time, there is only 5.
Continuity mistake: When SpongeBob scrambles into the Krusty Krab to tell Mr. Krabs the "good news", the doors swing wildly inward. When the two return outside and see the Flabby Patty, the doors have varied from being open inward, to being open outward.
Continuity mistake: SpongeBob is holding a picture of Plankton and Mr. Krabs, then when he pulls Plankton and Mr. Krabs together, the picture disappears.
Barnacle Face/Pet Sitter Pat - S8-E21
Continuity mistake: In "Barnacle Face", Spongebob is holding a glue bottle at the top of a ladder. When he climbs down, the glue bottle is not in his hand or on the ladder.
Barnacle Face/Pet Sitter Pat - S8-E21
Continuity mistake: In "Barnacle Face", Pearl throws a load of bars of soap at Mr. Krabs as he exits the room, leaving them scattered on the floor. In a few shots, they have disappeared.
Answer: I believe this is the Season 6 episode "Spongicus".