Corrected entry: When Bart first writes 'Treasure Island' on the board he has written it on two lines, the 'Treasure' is above the 'Island'. But after a couple of shots we see the blackboard again and the two words are next to each other.
Corrected entry: When Bart watches "Gorilla The Conqueror" with Homer, the giant gorilla in the film throws a tree at various people. Some of the people are in mid-air before the impact.
Correction: Not really a mistake in the Simpsons, more a nod to the fairly obvious, and poor, special effects used in these kind of movies.
Corrected entry: The flag outside Springfield Elementary remains still in the wind.
Correction: The flag is soaking wet and therefore too heavy to move in the wind. Perfectly natural.
Correction: The word "Treasure" is written above "Island" in all shots of the blackboard.
Super Grover ★