The Promise - S6-E13
Stupidity: Markham lets Ava call her uncle's phone, and she doesn't let on that Boyd answers instead. He later says "I don't trust anyone", but he didn't demand she put the call on speaker for transparency, he's quite happy (at the time) to just hear one side of the call.
He Lokomaika'i Ka Manu O Kaiona - S8-E20
Stupidity: After being stripped of their weapons while looking for terrorists in the jungle, Steve and Catherine meet up with Jerry, who has not had his gear taken, but didn't bring a gun because he's only a consultant. Some time later, after they open some coconuts using a small machete Jerry had on him, they hear gunshots, and go over to investigate, finding two dead hunters. They take a pistol of one of the hunters right before encountering the terrorists. So far, so good. But then to fight the terrorists, Steve has Catherine provide cover fire with the handgun while he attacks them unarmed, and hands Jerry a rock when he asks what he's supposed to do. Why doesn't one of them take the machete? You can still see it on Jerry's back.
Stupidity: Linda suffers a gunshot while in the hospital. The doctor calls for a trauma team that responds immediately to take her to surgery. The next time Linda is shown the trauma team is still taking her to surgery through the hospital hallways, and the whole Reagan family made it to the hospital and in the hallway as Linda is being taken to surgery. The hospital hallways must be long or the trauma team took the long way to surgery to allow the family to be there. (00:03:28 - 00:05:57)
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: Yoshi, Mario's sidekick who constantly follows him on dangerous adventures and has gone on dangerous adventures by himself, gets scared shitless when confronted by Riptor. This is not how Yoshi would act in a situation like this.
All Politics is Local - S1-E24
Stupidity: At the end of the episode, Joey and Melissa are in the kitchen, discussing Melissa's father. A small pot on the stove is very full of broccoli; almost overflowing. It makes no sense that Joey - who is a proficient cook - would be trying to prepare that much broccoli in a pot of that size.