At numerous points in the series, the phrase "Galley Grub" on the Krusty Krab menu is misspelled as "Gally Grub."
Squidward plays his clarinet straight out, like an oboe, instead of angled downwards.
Krusty the Crab throws a customer out of the Krusty Crab and the customer yells "My Leg!" while he is still flying through the air, yet to wound his leg.
Plankton's size varies throughout the series.
When Plankton turns the thermometer in the Krusty Krab, he turns the knob back and forth. The temperature goes down, not up and down like it should be.
The size of SpongeBob's bed varies throughout the series.
Errors in geography
The location of the Krusty Krab changes in various episodes. Most of the time, it is located to the left of SpongeBob's house. Other times, it's located to the right.
The geography in Spongebob's house and Bikini Bottom changes almost every episode.
The Graffiti that says "Nematoads are People too" should read "Nematodes".
In the episode where Spongebob is making his own Mermaidman movie, it is said that Patrick kept the lens cap on during the entire film, but, you can easily see that that is not true, since you see the camera filming without a lens cap.