House Sittin' for Sandy/Smoothe Jazz at Bikini Bottom - S8-E23
Continuity mistake: When Sandy finds SpongeBob and Patrick after wrecking the tree dome, the distance between SpongeBob/Patrick and Sandy changes constantly between shots.
Back to the Past/The Bad Guy Club for Villains - S7-E16
Continuity mistake: The Quickster was a member of the I.J.L.S.A in Mermaid Man and Barnacle Boy V. But in this episode, there isn't The Quickster in the I.J.L.S.A, but instead the Pi-Right Ponderer.
Fear of a Krabby Patty/Shell of a Man - S4-E1
Continuity mistake: When Mr. Krabs drags SpongeBob back into the kitchen, Squidward's facial expression changes between shots.
Karen 2.0/InSPONGEiac - S8-E28
Continuity mistake: Karen dumps a load of chum on a tray and some of the chum lands on the table. The chum that fell on the table magically disappears from shot a split second later.
Continuity mistake: When SpongeBob and Patrick see the map, a compass is seen next to it. As the two start touching the map, the compass has disappeared.
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.
Dying For Pie / Imitation Krabs - S2-E6
Continuity mistake: SpongeBob makes Squidward a tear jumper and there is a shot of Squidward sighing. In this shot, we can see no-one standing around the register. In the next shot, Mr. Krabs has suddenly appeared next to it.
As Seen on TV / Can You Spare a Dime? - S3-E5
Continuity mistake: When SpongeBob is making the patties at the end, he puts at least 20 patties on the grill. But just after he takes the buns out of the bag, there are now only 10 patties.
Mermaidman Begins/Plankton's Good Eye - S8-E22
Continuity mistake: When Plankton tries to open the safe, his arms come off. The arms stay on the safe. But when Mr. Krabs approaches the safe in the next shot, Plankton's arms have disappeared from the safe.
You Don't Know Sponge/Hide and Then What Happens - S8-E3
Other mistake: It is revealed in this episode that Patrick is right-handed. However, in the season 4 episode Krusty Towers, when asked to sign the Krusty Towers guest register, he is shown doing so with his left hand.
The Snowball Effect / One Krabs Trash - S3-E3
Continuity mistake: In "One Krab's Trash," after SpongeBob discovers the drinking hat at Mr. Krabs' yard sale, the two straws are connected to a cylinder with a hole. But when Mr. Krabs says "You were born to wear this hat!" the little cylinder has vanished. Later when SpongeBob is blowing bubbles, the cylinder has reappeared. (00:02:25 - 00:05:00)
Mermaid Man and Barnacle Boy IV / Doing Time - S3-E1
Continuity mistake: When SpongeBob zaps the pickles, he is standing next to the door. He instantly moves to the center of the room in a subsequent shot.
Chocolate With Nuts / Mermaid Man And Barnacle Boy V - S3-E11
Continuity mistake: After MermaidMan screams "To Make Out Reef" he accidentally falls over on his chair. When Patrick complains that they aren't gonna get pizza the chair is back up again.
Culture Shock / F.U.N. - S1-E10
Continuity mistake: When we first see Squidward in the canyon background, his outlining is gone. Then, in the next shot, it's back.
Other mistake: When SpongeBob has his picture taken, his tie is missing.
Other mistake: When Squidward opens the door to his house on Christmas morning, the door incorrectly overlaps the snow decoration on his house. (00:13:49)
Survival of the Idiots / Dumped - S2-E8
Continuity mistake: Dumped: When SpongeBob gives Larry the Snail dinner, Larry is sitting on two books placed on a chair. Then, as Larry smells the food, the bottom book is now facing a different direction. (00:19:54)
Other mistake: During the show's introduction in Seasons 1-8, when the kids chant "SpongeBob SquarePants!" for the second time, the whole screen shifts slightly to the left. As a result, when the lyric, "If nautical nonsense be something you wish" is sung, the far right side of the screen is slightly mirrored. Note how, when any of the four boats are at the right side of the screen, they are briefly duplicated. (00:00:16)
Other mistake: Rock Bottom: When SpongeBob sets up a cardboard version of himself and is shown sneaking to the bus, his holes are missing and he is perfectly square, instead of his usual sponge-like shape. (00:18:47)
Have You Seen This Snail? - S4-E3
Revealing mistake: After SpongeBob tells Patrick, "I can't find Gary," text that reads "Rough Draft Korea" briefly appears on screen during the bubble transition. (00:08:24)
Answer: In the "Christmas Who?" episode's intro, Patchy the Pirate is reading a letter where a fan ask if Spongebob loves Christmas as much as he does. Patchy explains they didn't always celebrate Christmas and this episode is a flashback to the first time Bikini Bottom had heard of Christmas. Santa had never visited before because nobody had believed in him before. Santa finally does visit because of Squidward's Christmas spirit. The "It's a Spongebob Christmas" episode aired 12 years later. So by this time, Bikini Bottom had been celebrating Christmas for quite sometime. Santa comes for a special visit because of how everyone in town, except Plankton, is on his naughty list.
Bishop73