Stupidity: Al tells Peg to hide the meat and cheese tray from Bud and Kelly. Obviously you need to refrigerate meat and cheese yet Kelly says I swear I smell cold cuts. Do we have any? Al and Peg both say no. They both have to see it in the fridge every time they open it.
A Bad Reflection on You - S1-E38
Stupidity: The decision to risk revealing their identities to Bulk and Skull is one that the Rangers could have easily avoided. Since they tell the bullies to cover their eyes and ears, under the false pretense of a magic trick, they could have simply teleported to the Command Center, or any other secure location, and then morphed, well away from prying eyes.
Until Sunset, the Full Moon - S1-E7
Stupidity: This is not quite 'stupidity' but rather a "movie logic", supposedly sharp deduction that is really just a wild and nonsensical guess. Zenigata knows for a fact that Fujiko is impersonating Elena because she knew right away where to get the first aid kit, while Elena hasn't been in the mountain house since her husband's death. That makes no sense; Zenigata has to assume that Elena was completely straight about that fact (if it was the treasure's hiding place as he suspected, she easily could lie), and a person can easily remember where they store their security items even after years, for a variety of reasons.
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.
Log 81: The Long Walk - S1-E14
Stupidity: They are looking for a red convertible. No other description of the car. A red convertible pulls up behind them and passes them. The ragtop roof is up but it's still matches the description. Doesn't faze them in the least.
Stupidity: Why do they always have to go through that washing machine setup in the laundromat when they have a great functioning elevator to the lab?
Suggested correction: Why would Gus go through the process of hiding the lab entrance stairs behind a washing machine but leave access to a freight elevator wide open? The elevator would be just as hidden and probably locked up. Not to mention it would be slower to take than simply walking downstairs.
Stupidity: An RAF officer is wearing a gold stripe on his shoulder boards instead of blue. On his lapels, he wore a corporal's insignia, and on his left pocket was an American colonel 's eagle. A soldier described as British was wearing American platoon sergeant stripes.
Zorro's Ride Into Terror - S1-E8
Stupidity: When Diego sees that the passage door is opened, he invites Sergeant Garcia to sleep in his bed. However, Diego never tries to close it, and in the rest of the scene, nobody (even Captain Monasterio) seems to see it open.
The Power of the Doctor - S13-E9
Stupidity: While on the Cyber planet in 1916, the Doctor receives a call from Kate Stewart telling her to come to Unit HQ in 2022 immediately, prompting her to then reluctantly ditch all her problems she's currently dealing with, to go to Unit. The TARDIS literally has all the time in the universe, so even if she waited a really long time, the problems in 2022 would still be there, so there was no need for her to change plans so abruptly.
The Stripper - S1-E3
Stupidity: The whole plot resolution can happen merely because, on top of Matlock's unbelievable guess on how to trigger someone's dormant personality - apparently murder wasn't enough, but a joke is - the transvestite has two entirely separate voices, one of which is a dubbed-in female one. Not quite believable even for the times.
Stupidity: The inspector knows that his house has been bugged; he does not know how many bugs and cameras are there, he just knows there are some. He does find a bunch of them with great ease when he gets back home - making you wonder how could he have ignored them to begin with, since all it takes is for him to raise his eyes, they are fairly big black cameras who do not camouflage at all for the most part. He then proceeds to make a phone call to the big baddie from his landline. Nobody in their right mind would do such a thing. Heck, you wouldn't want to use your home phone for such a call even if you didn't know that someone just put bugs all over your house.
Stupidity: Xander really has no reason not to believe Buffy when she tells him that Miss French is evil/a giant bug. There is an in-universe explanation of pheromones affecting him, but that's flimsy at best. He's already dealt with vampires and witches and body-swapping, and there has already been a murder around the time Miss French showed up... the fact he doesn't believe Buffy seems very forced and contrived.
Who, What, Where, Wendigo? - S2-E10
Stupidity: Dwight, Audrey, and Nathan all know Dwight's trouble is that all bullets are attracted to him, so why is he with them when they go looking for the killer, knowing every one is using a gun?
Emohawk - Polymorph II - S6-E4
Stupidity: On the walk back to Starbug, the Emohawk jumps on Lister's head to disguise itself as Lister's hat, but it leaves itself in its natural form whilst the crew continue to walk. The Emohawk is supposed to be disguising itself to fool the crew into making them think it is any everyday object. The Emohawk eventually changes into Lister's hat, but leaving itself in its natural form even for just a small amount of time could blow its cover. (00:18:15)
Stupidity: The Resistance is a rescue team that helps the various protagonists escape schools. They do this by leaving intricate hints that lead to a detour to the school alarm instead of going straight there, setting off the alarm and rescuing the protagonists.
The Best Burger in New York - S4-E2
Stupidity: Marshall says "The tiniest little burger joint you ever saw, tucked between a taxidermist and a triple-X bookstore."They could have just search all the taxidermists and triple-x bookstores and look for which ones are located together.
Stupidity: Right before the duel with Miss Fontaine, Jaden tells Jesse to sneak around and give the first aid to Blair. Rather than do exactly that, Jesse decides to stand behind Jaden and watch him duel for a few minutes, instead of going over to help her. He even repositions himself to be on Jaden's right, which would make it harder to get to Blair, even though his original position (on Jaden's left), would've made it easier for him to sneak around to her. (00:09:03)