Factual error: When the family is driving from New York to New Jersey, you see a highway sign for the exit for New Jersey. In the background is a Dofasco building which is in Hamilton, Ontario, very far from New York or New Jersey.
Factual error: No real archery instructor would allow Princess Mia or anyone for that matter, to shoot with people in front of the shooting line and that close to Princess Mia. And, the arrows aren't retrieved until all have been shot, not after every one.
Factual error: King Neptune's crown changes size when Plankton steals it and when SpongeBob and Patrick retrieve it.
Factual error: There is a scene where Lt. Grace Torres is showing her fighter aircraft to her younger sister Tina Torres and Maddie Dolan (the main character). Lt. Grace Torres calls the aircraft an F-15 Hornet. The F-15 is called the Eagle and is flown by the U.S. Air Force, not the Navy. The aircraft that is being displayed is the F-18 Hornet. Absolutely not a mistake that someone who flies the plane would make.