Sandy's Rocket / Squeaky Boots - S1-E8
Audio problem: When SpongeBob captures Mrs. Puff, her voice and the inflation sound are out of sync.
Continuity mistake: When Patar heats the squished crab in the fire, it's in his left hand. But in the next shot when he eats it, it's in his right.
Wet Painters / Krusty Krab Training Video - S3-E9
Continuity mistake: When Mr. Krabs Gets Home, there is a light switch by the door, but in the next shot there is a sign instead.
Krab Borg / Rock-a-Bye Bivalve - S3-E8
Continuity mistake: Rock-a-Bye Bivalve: When Patrick gets home from the party after midnight SpongeBob is angry, and as Patrick walks out in the interior shot the front door is wide open on the inside of the home, but in the next exterior shot the front door is wide open on the outside of the pineapple.
Mermaid Man and Barnacle Boy IV / Doing Time - S3-E1
Continuity mistake: Mermaid Man and Barnacle Boy IV: When SpongeBob runs into the kitchen with Mermaid Man's secret utility belt, the door swings open facing away from the grill, but when Squidward demands to know what's going on in the kitchen, the door opens the opposite way.
Nasty Patty / The Idiot Box - S3-E4
Continuity mistake: Nasty Patty: After the police officer cancels his Krabby Patty order, when he tells his partner they got a call about "two ghouls burying a stiff," Krabs' office door is missing.
Nasty Patty / The Idiot Box - S3-E4
Continuity mistake: Nasty Patty: When Krabs pushes SpongeBob out of the kitchen telling him to pour on the charm for the health inspector, the door swings opens at the left side, but when SpongeBob goes back to the kitchen to order one of everything, that door opens the opposite way, then the switch happens again.
The Bully / Just One Bite - S2-E17
Continuity mistake: Just One Bite: After Squidward buries the Krabby Patty and tells SpongeBob that he hates it, when SpongeBob walks to the back door of the restaurant there's a window to the right of the door, but when Squidward makes plans to sneak a Krabby Patty that window has vanished.
The Bully / Just One Bite - S2-E17
Continuity mistake: The Bully: When Mrs. Puff enters the classroom and apologizes for being late, the door knob is at the left side of the door, but in following shots it's at the right side of the door.
Club SpongeBob / My Pretty Seahorse - S3-E12
Continuity mistake: My Pretty Seahorse: After Krabs tells SpongeBob the restaurant is not a place for a live horse, when SpongeBob walks out with the seahorse the swinging door to the Krusty Krab's kitchen opens in the opposite direction than previous shots.
Continuity mistake: Rock Bottom: After SpongeBob and Patrick enter the bus, when SpongeBob asks Patrick if he has any change and for the duration of this shot, both the gear shift on the floor beside the driver and the open door of the bus have vanished, then they reappear.
As Seen on TV / Can You Spare a Dime? - S3-E5
Continuity mistake: As Seen on TV: After SpongeBob shouts about the grand finale he tosses all the food at the hungry crowd, and as they all happily exclaim, "Krabby Patties," there is only one door to the right of Squidward's order station in this shot, though there should be two doors.
As Seen on TV / Can You Spare a Dime? - S3-E5
Continuity mistake: As Seen on TV: The front door to Mr. Krabs' office is a solid door with an anchor on the exterior side of the door, but in a few shots the office's front door has a porthole window like other doors in the restaurant.
Krab Borg / Rock-a-Bye Bivalve - S3-E8
Continuity mistake: Krab Borg: The door to Krabs' office has a porthole in many shots, but after Krabs burns his eyes he rushes out of his office into the eating area, and when he runs past Squidward and SpongeBob the office door is the normal solid door, with an anchor on the exterior side.
The Lost Mattress/Krabs vs. Plankton - S4-E2
Continuity mistake: Krabs vs. Plankton: When Krabs meets with the attorney, Bottomfeeder, both the exterior and interior door knobs on his office door appear and disappear in various shots, even consecutive shots.
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Continuity mistake: Chocolate With Nuts: While SpongeBob and Patrick are selling chocolate, the elderly female's door opens at the left, but after Patrick claims their chocolate will make you live forever, the door is open the opposite way.
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Continuity mistake: Mermaid Man And Barnacle Boy V: When Barnacle Boy shouts that he wants to be called Barnacle Man and demands respect, the door to Krabs' office is missing. Then it happens again when the news comes on.
Have You Seen This Snail? - S4-E3
Continuity mistake: Have You Seen This Snail: After the customer asks for a refund it cuts to SpongeBob crying in the kitchen, and when Krabs walks in the door opens at the left side with no knob, but when Krabs tells SpongeBob that a problem can be solved with a little hard work, that door now opens at the right side with a door knob.
Something Smells / Bossy Boots - S2-E1
Continuity mistake: Something Smells: When SpongeBob walks into the kitchen the freezer door handle is on the right side, but when he opens the freezer door its handle is at the left side.
Hooky / Mermaid Man and Barnacle Boy II - S1-E20
Continuity mistake: Hooky: When SpongeBob is hooked the pointy tip of the hook is facing out, but when he asks Krabs what he should do, the hook is hooked into SpongeBob's pants the opposite way, with the pointy tip facing him. Additionally, he's hooked at the back of his underwear and pants, but when Squidward is holding the fishing pole the hook is at the front of the underwear, which are also perfectly intact despite being ripped off SpongeBob.
Answer: I believe this is the Season 6 episode "Spongicus".