Stupidity: Donna runs in to save everyone from the collapsing pylon, dying in the process, despite the fact that Superboy or Raven, both more powerful/resilient, could have stopped it falling without any issues whatsoever. Not even like anyone was distracted - the fight was over, they were all just standing around.
Stupidity: The super powerful Romulan commandos (no doubt with the help from the higher-ups infiltrated in the Federation) managed to touch up the footage of the fight in the roof so to remove every trace of the Romulan agents present. But Picard has been running, dodging blasts, ducking, and is knocked back by a huge explosion caught on camera and not deleted; we see it in this episode and it is unequivocally not caused by him. What is the point of going through subtly deleting every trace of the aggressors when it is transparent that something real happened and it's not all Picard's imagination? And the police simply take Picard back home from San Francisco to France without questioning him, not caring about investigating the explosion in the heart of the city involving a famous Admiral battling invisible enemies. If the conspiracy can erase anyone from the tape, why not erase Picard too, or the explosion and explain how he ended up K.O.'d differently?
Stupidity: The master goes through all the trouble of making Luke the vessel so Luke can go and kill several people and risk getting the attention of the slayer, when all he had to do is have his minions go out and kidnap a bunch of people and bring them to him and he could've fed off them himself.
Day 4: 11:00 P.M.-12:00 A.M. - S4-E17
Stupidity: When the couple is in the plant they call Jack on the cellphone, he instructs them to open the case and separate the book from the activation device. This was stupid, he should have told them to destroy it, since the codes had changed the moment Air Force One crashed, and it would take about 1 hour to make this work. This is explained later on in the show.
Stupidity: The brothers are angry at Leo because they say he's responsible for them dying because he chose to save other soldiers instead of them, Leo also blames himself for the same reason and says he should have stayed and gotten them out. But in the flashback it shows Leo helping them and then running off to help other soldiers, after he runs off the brothers are killed just a few seconds later. Even if Leo had chosen to stay with the brother he couldn't have gotten them out in time, the only difference would have been Leo would have died with them, but Leo dies in the same war so he didn't live much longer. Leo's guilt and the brothers' blame don't make any sense at all.
Stupidity: On 8/12/04, Hope specifically told everyone that when the coin was thrown into the force field, there would be a bright flash and that they shouldn't look at the forcefield when this was done. But all three times that the coin was thrown at the force field that day and the next, everyone looked right at it the whole time, and then recoiled in pain at the flash that inevitably occurred.
Norman Mailer, I'm Pregnant! - S5-E6
Stupidity: Luke arrives at Lorelai's house. He comments that she left her car light on. Lorelai then tells him that she left it on because the porch light is out. He says that the battery is going to die. She tells him that she has it timed out perfectly. She then says that there will be 2 hours to spare and that the car has all day to charge. Cars don't charge unless they are running. Is she really going to run it all day? Why didn't Luke point out the error in her logic? Doing so is staying true to the character. The oversight is glaring.
Stupidity: Paulie and an associate just killed 2 drug dealers or stash house guards, and they are rummaging throughout the apartment touching appliances and other surfaces without any gloves. Paulie was previously arrested and did time so his fingerprints are on file. Paulie also used a knife to stab one of the Colombians without any gloves on, and he just left it in his body. The police would have no problem linking him to this crime within a week after forensics did their sweep. (00:03:00 - 00:04:17)
Stupidity: When Brass and Sarah enter the locked storage cellar where the boys are hidden, Greg, a graduated rookie, straggles along behind them when he should have known better to stay put. As anyone could have come along and locked that cellar door behind them, trapping them inside.
Stupidity: After the accident, Dawn is in spirit form on the road trying to wave down an oncoming car (driven by Martha Kent). Dawn doesn't know she's a spirit that can pass through objects at that point. Since Martha can't see her, she keeps driving straight towards Dawn. Dawn sees the vehicle isn't slowing down and instead of simply stepping out of the way to avoid getting hit, she turns her back, revealing to the audience that objects can pass through her now.
Stupidity: After Walks on Cloud releases Dr Mike, she runs off and hides in a wild thicket as the Dog Soldiers and One Eye look around the area for her. A pair of buckskin are then seen scoping the area, then walking off as Dr Mike leaves her hiding spot and gets 'surprised' by One Eye, who knocks her out. She should have known better and stayed put until sunrise, as Sully taught her when it came to the Cheyenne war parties.
Girl Trouble / School Dance - S3-E18
Stupidity: Girl Trouble: Helga pulls a nasty prank on Arnold in class by gluing feathers to his bottom. Mr. Simmons sees this, but for whatever reason, does not give Helga detention for it. The next day, Helga spills paint on Arnold, then he throws some on her as revenge. Mr. Simmons sees this and gives Arnold detention even though he was simply fighting back at Helga for pushing him too far. Perhaps Mr. Simmons' brain was on vacation those two days. (00:03:16 - 00:08:42)
Stupidity: Characters repeatedly make note of how hard to kill the Wraith are, but sometimes, especially in the final episode(s) of season 1, they go down easily in a few bullets each, and then don't even regenerate as the characters turn their attentions elsewhere.
Suggested correction: It's explained that Wraith are easier to kill the less they've fed recently, and that in later seasons, with more and more Wraith waking up, fewer and fewer are getting chances to feed before they fight the Atlantis Team.
The Best Thing That Ever Could Have Happened - S5-E13
Stupidity: Miss McCluskey asks Eli who's going to fix her water heater now. Do we need to remind her there's some guy named Mike Delfino who lives right next to her and is a plumber?
Stupidity: During the scene at the restaurant, Rose pulls the fire alarm. Then she and the doctor run through the kitchen, past several chefs who just duck and crouch into corners. This would easily be one of the stupidest ideas ever. If there was a fire, they would evacuate out the back door instead of just sitting there waiting to be choked to death. And if they knew about Auton Mickey, running out the back door would also be a lot more logical than just crouching down and waiting to be battered to death.
The Night of the Firebrand - S3-E2
Stupidity: West is introduced to, then knocked unconscious by Vixen as she hides a club behind her back. A trained Secret Service agent like West would not have let his guard down in this situation, as the entire fort was awash in bad guys.
Stupidity: When they are conferring before surgery everyone is keeping scrub except for Avery who has his arms crossed. Shortly afterwards you can see him look around at all his co-stars, realise he screwed up and try to casually raise his arms. (00:15:00)