
I'd Rather Twitch Than Fight - S3-E10
Stupidity: Like most dilemmas on the show, the controversy could have been resolved by witchcraft without Darrin knowing. Why didn't Samantha just twitch a duplicate tweed coat?

Stupidity: Despite being a high-profile fugitive who was a local celebrity in his previous life, Saul does very little to alter his physical appearance, settling on just a mustache and glasses. Growing a beard, wearing a hairpiece, and altering his speaking voice around others would have gone a long way in preventing him from being made.

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)

Stupidity: The whole episode revolves around Adam bringing his girlfriend Emma to his parents' house to meet the family, but problems start to arise when Emma's sister begins texting Adam pictures of her in her underwear. Adam is extremely bothered by this and attempts to make sure Emma doesn't find out. When everyone is at the dinner table, Adam decides to leave his phone out on the table even whilst he continues to receive texts from Emma's sister and the family begin to comment on it. If Adam was so concerned about Emma finding out about the texts, he could have easily turned off his phone and put it back in his pocket, but instead decides to leave it out on the table and switched on, only drawing more suspicion from Emma. Even when the little girl arrives later and asks to play with his phone, Jonny reaches out to grab it, but all Adam does is take the phone off the table so Jonny can't reach it, and then immediately puts it back on the table again.
Suggested correction: Adam knows Jonny is joking with him, as he usually does. As for Katie taking his phone he didn't expect her to. They have all seen Adam's reaction when getting the messages and he is trying to cover something up. Doing anything to prevent anyone seeing his phone more would arouse suspicion. Personally I don't understand why he didn't just explain that Emma's sister has been sending him pictures and ask Emma to talk to his sister. He didn't do anything and loses someone he liked for no reason.
I was mostly referring to the scene where they are sitting at the dinner table BEFORE Katie arrives. Despite the fact that he kept receiving texts from Emma's sister and was growing more concerned and everyone begins to comment on it, all he does is put it back on the table, switched on, ready for another text to come through, which makes everyone further suspicious. There is no reason at all why he couldn't just turn off the phone, put it back in his pocket, and lowered suspicion.
A better idea would be for him to have told Emma after it happened the first time. I'm sure that saying "your sister just sent this to me for some reason. I'm quite uncomfortable. Could you please ask her why she's sent me this?" would have sufficed. He creates bigger issues by denying anything is happening.

First Kiss - S1-E2
Stupidity: When Jeff Malone leaves the sandwich shop, he leaves the sandwich on the table. It would have been very easy for them to tell what was on the sandwich without needing to wait for Max to get home to recreate it. (00:02:41)

Stupidity: When Eddie finally finishes installing the VCR and it explodes, they get a man out to repair it. However, Eddie had previously told Richie that he'd stolen 60 VCRs; 17 in the living room and another 43 in the attic, so they could have used one of the other 59 and saved themselves a crate of Malibu.

When in Rome - S1-E3
Stupidity: A supposedly covert camera is placed in plain sight on a wall in a crowded room, with a prominent antenna showing, and a blinking blue light. (00:16:55)

Stupidity: In the flashback, Emily's sister takes ill while playing her flute. In the next scene, the sister is sick in bed and Emily now has the morpher around her neck, but she is in the exact same outfit. If the sister was forced to pass the legacy on due to disease, it should have taken more than just a few minutes or even hours to learn that.

Stupidity: For their set list at regionals, Schue chooses a medley of Journey hits. Since his kids are considered the competition's underdogs, and it was pointed out to him in the previous episode that Vocal Adrenaline's weakness is funk music, he should have used that info to New Directions' advantage.

Is Lupin Burning... ?! - S1-E1
Stupidity: Despite the fact that there are 100 (literally) cameras around the racing circuit and (again literally) everyone from the staff to the fellow racers works for the Scorpion gang, Jigen and Lupin's switch can happen without anyone noticing, even if it involved racing side by side for a lengthy period of time.

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)

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: In "Studio Stoops," one mobster ties Larry to a bed and another mobster ties Moe to a chair. The second mobster says, "Boss, why don't you let me plug 'em?" The other replies, "It would make too much noise. Wait till we get 'em outside." If that is the plan, then why tie up Moe and Larry indoors?

It's Not Easy Being Green - S5-E16
Stupidity: Unless the tow truck was someone else's or Hank had the keys surely Dale and Bill could've used it to drive Boomhauer's car back.

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: 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.