In Korea Sponge Bob is referred to as "Square Square Sponge" or, quite often, "Square Square Sponge Song" (in the title song they needed four words to match the music and most children refer to him the second way).
Spongebob's last name is Squarepants but all of his relatives are round exept Stanley who is part square as it is revealed on the episode "Stanley s. SquarePants" (2007)
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.
When Plankton is turning the thermometer in the Krusty Krab, you can see he is turning the knob back and forth. Yet you see the temperature is just going down, not up and down like it should be.