Stupidity: The protagonist has a sophisticated alarm system with cameras...that do not properly show who is at the gates (the cameras are positioned in a way that does not show the face of the person ringing). The bad guys are disguised as police officers...and wear ski masks, which would have made the disguise entirely pointless - but luckily for them, Nicholas Cage can't operate cameras nor looked at the ones on the entryway or the front of the house, didn't open the door sooner nor peeps before opening. They could not know any of that, though, just that the camera at the entrance has a terrible angle.
Stupidity: To quietly kill the hotel valet he is replacing, Diabolik throws a knife at him from distance, hits him in the back, and then drags his body in the middle of the street to the nearest manhole, leaving a long streak of blood he does not conceal. If this sounds pretty risky and unsafe especially for a meticulously planned murder, you have also to consider that in the comic book from 1963 this movie otherwise faithfully adapts, Diabolik did nothing this foolish; he quietly killed the guy strangling him next to the spot he'd dump his body into.
Stupidity: I seriously doubt that any Mexican Mafia cartel operating here in the U.S. would waste their time eliminating two simple patrol officers. There's nothing to gain by doing so, and it would bring a war between themselves and the police, which in return would bring hundreds of arrests of key members, drug busts, raids of their operations within Southern Cali, etc. They wouldn't risk their business taking millions of loss of revenue all to kill two patrol beat cops.
Stupidity: The metro police officer (and co-conspirator) went to the old cement factory where the other bank robbers were. Since the police officer (accomplice) wanted the money and did not want other police officers to be nearby, he called 911 and made an anonymous false report stating he spotted the person police were looking for and misdirected them further away. Maybe a good idea, but he made this call using his own cell phone. (01:12:20)
Stupidity: Angela ran over to her neighbor Mr. Charlie when she heard him come home. Angela was complaining that his son and friends make too much noise, do whatever the want, are bringing property values down, act wild/crazy, draw attention to everybody, and she doesn't want the police coming. These may be legitimate complaints, but the way Angela expressed them would bring down property values! Not only was she yelling in the street, she used "m-f-ing" several times, as well as other select words. (00:02:35 - 00:03:07)
Stupidity: The protagonist knocks at every door, humiliates himself, losing any hope of getting his dream job, jumps through all sorts of hoops to get a court order to save Crawford's wife, but somehow, once he gets it, he has to drive through LA and physically get to the hospital room where euthanasia will be performed, because he couldn't be bothered to phone the hospital to tell them about the court order or talk to someone in the lobby.
Stupidity: A movie always needs extra conflict, but Julie's reasoning for walking out on Marcus and Mike is one of the dumbest. "If his wife can find us, I'm a LOT better off on my own." What sort of logic is that? She's the wife of his best friend. Of course she knows where he lives. (01:32:45)
Stupidity: Just after Ricky has beaten up Tarzan, the warden has the ceiling of the cell Ricky is trapped in lowered in an attempt to crush him. However, earlier in the scene, Tarzan made a huge hole in the wall of the cell to get into it. The hole in the wall is even visible in the background when the ceiling begins to lower. Ricky could have simply run out of the hole in the wall to get out, rather than try to hold the ceiling up with his bare hands. (01:02:48)
Stupidity: The Foot Clan found the Turtles' hideout in the sewers thanks to one of their members who followed Raphael when he was carrying an unconscious April O'Neil after he saved her from the evil ninjas. When Shredder later is trying to find the Turtles, it takes Danny's betrayal to point him towards April. How stupid does he have to be? It's a connection anyone would have made, it was the second time she was saved, even.
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: In the bar scene, Jack gets into a fight with a guy he busted a few years back, then Reggie turns to the bartender and asks for a gun. The bartender hardly hesitates and hands it over. There is just simply no scenario where a bartender would hand a loaded gun to a patron they had just met.
Stupidity: When they raid the warehouse as the criminals are trying to leave town, they load the girls into.a white van. A man (Bruce Willis) wearing a ski mask gets out of the passenger side and covers with his pistol as they load the girls into the van. The entire time the slide on his weapon is back, so the gun is not ready to fire.
Stupidity: After Casi changed the tracker on the Navigator, he was sneaking between vehicles to get out of the tow pound. The Whale came and stood in front of the two vehicles Casi was between. Casi stood up and, instead of turning around and running away, rushed TOWARD The Whale in an attempt to get past him. The Whale, much bigger, threw Casi against a vehicle and then onto the garage floor. (01:03:34).