Stupidity: Damon and Stefan are trying to get Elena's humanity back - they could have just asked Rebekkah or Klaus or Elijah to compel her to turn it on.
Laura Ingalls Wilder (1) - S7-E1
Stupidity: Charles and Caroline are dancing at the church social. Charles makes a comment about Laura getting married. Caroline responds with "I'm just dying to call you Grandpa." Mary's son just died. Charles has already been a grandfather. That comment was beyond insensitive, and just plain stupid as written. She should've said, I can't wait to call you Grandpa again.
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.
The One With All The Rugby - S4-E15
Stupidity: Emily tries to help Ross inflict pain on the other rugby players and tells him about one player who doesn't wear a cup. No one who knows rugby would ever wear a cup, it is more hazardous than helpful to wear a cup in rugby as it involves a lot a grinding, and a simple slip or movement could cause serious damages to the male genitals. Especially if these guys are British and well versed in rugby which they are.
Episode #1.7 - S1-E7
Stupidity: When Eugene approaches Tsuda after Tsuda is shot by Ae-sin, Tsuda attempts to shoot him, but after pulling the trigger, he realises there are no bullets in the gun. Seconds later, a group of soldiers run up to him, and he attempts to shoot them, but he can't because the gun is still not loaded. Something he should have known since he only just attempted to shoot Eugene and failed because of it. (00:50:00 - 00:50:30)
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)
The Pin-Up - S7-E17
Stupidity: After Erin leaves with the military captain to Camp Lee, John and Maryellen turn around to see John Curtiss nowhere around on the porch where Maryellen left him. So John goes off to look for him, while Maryellen goes in to check The House. John Curtiss is a one-year-old baby who couldn't open a door.
Stupidity: S52 E82 Nate sets out to contact Damian for Amy, Damian's mum. Nate has never met or seen Damian. It turns out the man he meets is not Damian, but a man posing as Damian. Since Nate has never met Damian, it would have made sense for Nate to have looked at a photo of Damian before the meeting. (00:11:08)
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.
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.
The Signs in the Silence - S6-E21
Stupidity: Bones realises she could pull a wisdom tooth from Amy in order to identify where she grew up and find her birth parents. Which works, but at no point do they consider simply going through missing person records with the relevant info. They know how old she is, they know roughly when she disappeared, not like there are hundreds of 3 year olds going missing every year, especially not with Waardenburg syndrome. By that age her deafness would have been apparent, which would narrow the pool hugely.
The Perks of Not Being a Wallflower - S1-E3
Stupidity: Superman finally smashes the weirdly strong bad guy through a wall, then goes to Lois, says "he's gone", and whisks Sarah to hospital. But he has no idea if the bad guy is "gone" or not - they've just had an epic fight, he has some sort of super strength / resilience, and for all Superman knows he'll come around in 10 seconds and finish the job of murdering Lois.
Suggested correction: Superman knows the 'strong bad guy' is close to his own strength. After fighting him, he knows what effect the crash through the wall would have had on him, if he was knocked out, and how long he would be out for. So he knew there was little risk of the guy coming around in 10 seconds. Alternatively, he X-ray scanned the area and saw the guy was no longer there.
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.