Stupidity: After Josh runs away from home after being turned into an adult, nothing seems to be done about his "disappearance." The only indication that he is missing is his picture on the back of a milk carton. There's no flyers about him missing. No mention of his disappearance in any newspapers or TV news about his mom saying that he's been "abducted" by a stranger. Even when Josh writes a letter home, he uses the actual address of where he's staying, but no cops turn up at his door after his mom receives the letter.
Stupidity: Ghostface ambushes Sidney and her friend with the two detectives protecting her while in the car. Ghostface busts out of the driver window, and slashes the throat of the driver detective and then assaults his partner, kicking the crap out of him. Ghostface is obviously going with the intent to kill and has a weapon. He just killed one of the detectives and threw the other in the street in front of the car. When Ghostface jumps in the car to take off, the living detective, beaten, jumps up with his gun trained on Ghostface. But rather than do anything smart, he just yells at the killer, the cop killer, to freeze and get out of the running car that he's standing in front of. He just saw the guy kill his own partner and knows he is intending to kill the girls in the back. His gun is pointed at Ghostface who is about to drive over him, but he just yells at him instead of shooting.
Stupidity: When Jasmine finds out that Prince Ali is actually the boy she met in the marketplace, she seems to completely forget about Jafar telling her he had been executed. She never asks why he's alive, nor does she even bother to confront Jafar about his treachery.
Suggested correction: The fact Aladdin was alive only told her Jafar lied about it. When she is brought back by Aladdin to the palace it is still night, not long after that she is confronted by her father and Jafar who has him under a spell. She hardly had time to ask about the treachery, probably thinking to do it in the morning. It is there and then Jafar is exposed by Aladdin. She probably wondered about it, but didn't figure out the implications yet.
Stupidity: In 300 years, in an empoverished world full of people hungry for techs, nobody ever tried to remove the ship from a small pond barely 15 feet deep, and everything inside seems intact. It is mentioned that few tried because the technology is hard to sell being unknown (which is laughable), but surely some would try to strip the ship for alloys, and certainly the lights and monitors wouldn't stay untouched in a world based on scavenging. For 300 years and so close to the city, even.
Stupidity: Colonel Sharpe retrieves a gun from a locker on the Freedom shuttle. However, said gun is shown lying flat on the floor of the compartment, with no visible means of securing it, which would hardly be standard NASA procedure given the shuttle undergoes a high-G launch, orbital manoeuvres and various other high acceleration events. A loaded gun bouncing around is the last thing anyone would allow on a shuttle. (01:42:39)
Stupidity: When the birds gather in the schoolyard, Melanie runs in to warn Annie. Rather than calling the police or fire department for help and then shelter in place until aid arrives (which would take about ten minutes), they instead decide to make a run for it with the children, out in the open, getting attacked by the birds. As it's the 1960s, the schoolhouse presumably has a working phone.
Stupidity: Dafoe does a lot of looking around while flying the plane. He could have pulled up much sooner. Then he screams and puts his hand to his face, and then he sees the tower and crashes into it. (01:53:29)
Stupidity: At the outdoor market, Libby told her old girlfriends that she'd "be right back" and went into a stall in the women's room. Soon, her girlfriends came in but stayed in front by the mirror. Without bothering to look if anyone (particularly, Libby) was in one of the three stalls, they started talking negatively about Libby (e.g, " Ugh, what is it about her that is so irritating?", "I feel sorry for her", "She looks like she's wearing a Halloween costume", "She's like a lumberjack"). (00:55:08 - 00:56:00)
Stupidity: Given his speed, surely Superman could've stopped both missiles with no problem.
Stupidity: When Cougar (and later, Maverick and Goose) report to Stinger's office at the beginning of the film, a photo of an F-5 in flight (or possibly a T-38) appears on the wall beside his desk. However, the F-5s that appear in this movie are standing in as MiGs. Of all the aircraft photos the set designer could have selected for this scene, it seems strange to use one of an "enemy" aircraft.
Stupidity: When Matt goes to the bank to close out the account he learns that it's been closed already by Kelly. Matt says he will be expelled, but he never did anything wrong except lie about who Kelly was. The bank teller is the one who was flirting with him and gave him the money with out any proper ID or papers, so if anything the bank would reimburse Matt/the school.
Stupidity: All of Robbie's circuits have been burned out as a result of Morbius ordering him to kill the Id monster. The crew only has 24 hours to get the ship loaded and a safe distance away from Altair IV before it explodes. But one or more of the crew spends the little time they have fixing Robbie, a very sophisticated piece of technology, who is working the controls at the end of the movie.
Stupidity: Paul Manfield (Arthur Pope) and his family have been hiding from and eluding the FBI for fifteen years, but Paul gets so intoxicated one night that he loudly sings "Pretty Woman" walking toward his house - where neighbors could hear - and yells that he is not Paul, he is Arthur Pope. (00:52:18)
Suggested correction: People do seriously stupid things when they are drunk, and Manfield/Pope is very, very drunk.
Stupidity: When Gail shoos Luke off the first day, in fact nobody accompanies him to the door and they discuss the evil plans when he's not even gone nor they even check he is, they just go ahead with the script. It's a rather odd dynamic, very rushed and movie logic-like. Or theater logic, since it's a typical 'exit stage left' moment.
Stupidity: When seeing that the bridge is out, JLC could've easily climbed out of the sunroof and hop off the back of the limo and onto the pavement, suffering a few cuts and bruises at the most. I know that it would've been anticlimactic, but still.
Suggested correction: You're assuming that jumping off a runaway car is a simple task that anyone can do. She's scared out of her mind, and many people in a similar situation would probably be scared at the prospect of jumping off a moving car, even with the knowledge that they will be flying off the road shortly.
Stupidity: When making apple sauce, just slapping a paper lid on the jar (instead of canning it properly) , would soon result in the jars turning to mold.
Suggested correction: We see Ariel sign in English, but most likely they have an entirely different alphabet and language from our own.