Stupidity: Medusa is the queen of the secret kingdom on the moon. She knows that they are very secretive and keep hidden from the humans on Earth who would have no idea who she is or that there are secret people on the moon. And yet in Hawaii, she walks up to an ATM and tries to demand by voice commands it give her money, saying, "I am Medusa of Attilan, and I need money." It is extremely stupid of her to think a random ATM in Hawaii would know who the secret queen of a secret moon base is.
Stupidity: Whilst Reva is running across the rooftops, there is a moment where she does a backflip in order to propel her forwards towards the next rooftop. If she was attempting to jump between roofs, then doing a backflip would not have been useful as it would only slow down her momentum instead of build it. (00:25:28)
Will the Real Martian Please Stand Up - S2-E28
Stupidity: The whole plot is based upon 6 people not being able to spot the seventh (odd man out). We can eliminate the couples, the driver remembers the pretty blond getting on the bus and the crazy old guy would stick in anybodies memory, so it leaves only the sour old guy in the coat and hat as the martian.Also all the troopers has to do was ask for IDs which they do but quit after they ask the crazy old guy for his.
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: When the new principal is addressing the student body, Avalanche tries to impress Kitty by causing a couple of small earthquakes, one of which causes the scoreboard to crash to the floor below. The principal laughs off the incident and continues to address everyone instead of either evacuating the area or having everyone take cover.
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.
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.
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.
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)
Tag Team Trial: Part 2 - S1-E11
Stupidity: After Jaden summons Elemental Hero Sparkman to the field, he also activates the spell card Spark Blaster, which he equips to Sparkman so that it can change any monster on the field in attack mode to defence mode. He decides to switch Gate Guardian to defence mode, however, he could have also switched Defence Wall to attack mode as well. Then he would've been able to have Sparkman attack Defence Wall, and it would have been destroyed since it has 0 attack points.
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?
Stupidity: At the start of the episode, the Brunnen-G planet is about to be under attack by His Shadow in a big ship that is capable of destroying the surface of the planet and everybody on it in under a minute with its fire power. It seems the Brunnen-G had time to respond, seeing as they send a counter measure against His Shadow... Except that they only send a single squadron of 6 fighters. Their planet is about to be obliterated by His Shadow's killer ship, and they only send up 6 fighters. And of course, they fail and all die except for Kai. (00:01:45)
Stupidity: The last remaining Xindi, in desperation, attempts to release the virus over the fan, despite the virus not being fully ready. However, it seems the only reason he didn't release the virus at that time was he had to seek cover from Archer and T'Pol shooting at him and to start shooting back at them. However, he had plenty of cover from the rooftop stairwell, which was right next to the fan, and he had enough time to dump out the contents over the fan.
Stupidity: When Jonas says he saw a creature go through the walls, people want to assume he must be hallucinating. Yes they sweep the base, but Carter questions its ability to pass through solid matter as if she's never seen that happen. When Jonas sees a creature again on the device with Carter there, she gives a look like he's going crazy rather than at least try to use a TER to scan for it. Plot wise it seems this is done just so O'Neill can leave the base and spread the "infection."
A Rough Whimper of Insanity - S1-E7
Stupidity: The hacker's VR goggles are not plugged in to anything (despite having a wire for this purpose) when he and Tom sit down at the computer in the teacher's house.
Stupidity: An explanation is given for the reason why the bombs planted on the Gundam are not activated by remote control (they have plastic explosive in the regiment but not remote controls!), but no reason why they set the timer for the explosion to 30 minutes, way too much to be of any use in combat against the Gundam. Moreover, if the vulnerable spot of the Gundam shield were situated where it explodes at the beginning, it'd be completely useless.
The New Original Wonder Woman - S1-E1
Stupidity: There's much fuss about who will take Steve Trevor back which is resolved via a contest. Why the Amazons don't heal him, if possible, then set him adrift to a safe port is never asked. They did this when Nazis invaded in the two part episode The Feminum Mystique.