Best fantasy movie mistakes of 1988
Revealing mistake: Any time when the two girls are in hell's corridors and running around, you see these corridors as stone walls, yet whenever they back up against one of these walls, you can clearly see they are merely rubber sheeting overlayed on a framework as the rubber sheeting bends and contracts very clearly.
Continuity mistake: In the scene where Tom Hanks goes back to his mother's house when he's "BIG", he tries to convince his mother it's him by telling her his birthday: November 3rd. However, in the scene (with John Heard and Elizabeth Perkins) showing the milk carton of Tom Hanks "missing" as a young boy, his d.o.b. is shown as 1/20/75.
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).