Factual error: When Peevey gets stuck in the truck, Cliff fires up the rocket pack and simply pushes it clear. If the rocket pack can push out enough thrust to move a 2 1/2 ton truck, Cliff's body can't take that kind of stress. He stretches his arms out, starts pushing, and sets off the rocket, putting himself between the truck and an accelerating rocket demonstrably capable of moving it. The truck is stationary so has 2 1/2 tons of inertia. The rocket instantly accelerates it to an appreciable speed. Human arms cannot take that kind of stress. He's going to be crushed.
Factual error: When the whole Banks family sits down to dinner, George asks 'Who wants to go to a Laker game on Thursday?' According to the timeline of the film, this is sometime in August, and the Lakers are in off-season.
Suggested correction: When George goes to the grocery store, you can see Halloween decorations.
When they first meet with Franc, he says that the wedding is set for January 6 and that gives them five months. So it is definitely August at that point.
Factual error: In one scene, Vada is showing off her mood ring. The movie is set in 1972 and mood rings were not created until 1975.
Factual error: There's a scene where Belle's father is riding away in the snow on his horse - the tracks left behind by the horse are exactly backwards. The round part of a horseshoe is at the front, not the back. (This was a deliberate 'in joke' done by the animators.)
Factual error: The movie is set in the Middle Ages. Therefore, the traders who come to the Winterland to sell their goods must be quite ahead of their time to carry fairly modern lighters. (00:04:20)
Factual error: In one of the train cars on the way out west, upon being asked by one of his henchman, "When are we going to eat the mice?" Cat R. Wahl replies, "Which would you rather have, the crouton or the entire Caesar salad?" Caesar salad was not invented until the 1920's and the movie takes place in the late 1800's.
Factual error: At the end of the Mamushka, Fester catches the final knife down his throat. With the length of the blade and the angle at which the knife is in his mouth, the point of the knife should be coming out the back of his head.
Factual error: In the scene inside Channel 3's open space, there are several wall clocks, but they are wrong. When it's 10:05 in New York it's not 3:05 in Frankfurt, London and Paris; besides, 3 clocks out of 6 which always point the same time is really wasteful - not that London is in the same timezone as the other two, but here they all point at the same time. (00:37:25)