Stupidity: When Libby finds out her husband is alive in San Francisco, she calls the insurance company to tell them. Why didn't she call her lawyer who could have looked into this and actually done something about it?
Cynthia Gurski
Stupidity: It's stated that Imhotep will fear cats until he has fully regenerated and two different scenes show him fleeing in terror at the sight of a cat. Despite this, none of the characters that Imhotep is trying to kill that are fully aware of his weakness even think to have a cat with them at all times.
Phaneron
Stupidity: Al is supposed to be a super serious toy collector and seller, but he handles valuable toys without cleaning the cheese puff dust off his hands.
wizard_of_goreSuggested correction: It's also established someone is coming over to clean said toys, dust included, and when he does the handling, he's just been sharply awakened by the TV therefore is off-kilter.
dizzyd
Stupidity: Not much point in having a purpose built workshop for a speedboat 4-5 floors above river level. As shown later in Spectre there were underground moorings and easy access to the Thames at river level.
Suggested correction: At the time of release of this film it's safe to assume that there might not have been easy access at river level.
Ssiscool
Stupidity: Dr. Horniker (MD, PhD) advised Mr. And Mrs. Lisbon that Cecilia could use a kind of "outlet outside the codification of school" and should "interact with males her own age." The Lisbons did arrange a party for Cecilia, but the boys who were invited (or came) were somewhat older. Cecilia, at age 13, would be in Jr. High School. Tim and Parkie were 16-17. Chase looked a little younger than the other boys, but none of the boys were really "males her own age." Had the boys been 12-13 or even 14 and Cecilia's older sisters not present, Cecilia may have a better experience - and not jumped to her death during the party. (00:07:35)
WHAT?