Factual error: The picture of Eddie and Teddy on the road with dad, supposedly taken in 1906, shows a Ringling Bros and Barnum & Bailey circus poster. In 1906, the Ringling Brothers circus and the Barnum & Bailey circus were two separate circuses playing in different parts of the country. They did not combine the two shows until 1919. (00:27:00)
Factual error: Although the film is set in 1962, it uses the song "You Don't Own Me" which wasn't released until 1963 (and didn't become a big hit until 1964).
Factual error: At the end, when Cyndi Lauper touches the glowing pyramid, goes into a trance, and starts translating the inscription, Jeff Goldblum pulls her off and she doesn't finish it. One of the bad guys says that what Cyndi already said will be enough to help him decode the rest and that it's just a matter of "cartography" now. He should have said "cryptography" (skill of decoding secret writings) and not "cartography" (which has to do with making maps).
Factual error: When Jack is trying to buy the bus tickets, the bus company employee tells him that his credit card was cancelled. Credit card companies do not divulge that type of information, they simply indicate whether the requested charge is accepted or denied.
Factual error: The pizza parlor's big break comes when the Fireside Gourmet features them on his TV show. Leaving aside the unbelievability of a gourmet restaurant critic visiting a pizza parlor, he appears as himself on his TV shows. Food critics always dine anonymously so that the restaurant can't give them any special treatment. (Movies love to mess this up.) In addition, when they watch his review, he's barely spat out the name of the restaurant when the phone already starts ringing. Barely enough time to dial the phone, let alone look the restaurant up in Information as most would have needed to do for this little-known place.
Factual error: The address on Claire's business card reads 514 West 43rd St. When Frank gets there, the street sign is for 3rd St./900 East block. The sign on the building reads "9th Street Temporary Shelter". Along with these discrepancies, taking into consideration that 3rd St. may be the cross street, WEST 43rd would not cross 3rd St. EAST, as they are on opposites sides of Manhattan. Even if the '4' on the sign for 43rd St. were somehow obliterated, 514 still would not be on the 900 East block. (00:53:10 - 00:54:15)
Factual error: When Judge Reinhold is in the department store playing the Space Invaders video game, and one of the men chasing the skull comes to talk to him, Judge continues to play the game, so the man stands between him and the screen in order to get his full attention. If you watch the screen, the game actually continues to play on.
Factual error: There is no way the DMV will pass one twin based on the fact that his twin passed, even though they ended up taking his license. The mistake was giving it to him in the first place based on the fact his twin passed.
Factual error: The damage done by the hobgoblin-induced fantasies is real, as seen several times in the movie. Kyle's car runs off a cliff, Nick's grenades really explode, etc. Nick is in one scene set ablaze by throwing himself on a grenade, and is completely engulfed in flames from his head to his toes. But he shows up in the last scene with nothing but a few minor burns on his forearms and a pair of crutches (that he immediately discards). His hair and eyelashes are not even singed.
Factual error: When Johnny shoots the taxi with some kind of cable and pulls it backwards, the rear tires are shown to be spinning in an attempt to move. The taxi is a Chrysler K-car which is front wheel drive.
Factual error: When Arnie and Devito are stealing the car and Devito sets off the car alarm, Arnold picks up the car from the back end to stop it. If you watch the wheels you will notice that they don't shake or move at all when Arnold sets the car back down on the ground. (00:27:23)
Factual error: The sequence showing the moon is incorrect as it shows the Moon as it looks from the northern hemisphere. It should be inverted.
Factual error: When John Candy throws alcohol on the fire after his bear story, there is a big explosion, but no amount of alcohol could cause an explosion big enough for a mushroom cloud, only gas or lighter fluid (especially the only small amount that is in John Candy's glass he's holding the glass is barely full and mostly ice.).
Factual error: For most of the movie you can see mountains and large hills in the background. The movie takes place in Kansas and almost all of Kansas is flat.