
Stupidity: A prisoner, Jack Williams, rats out Hogan and his team to the Germans, so they fake his death and smuggle him back to London for court-martial. What a stupid thing to do. They should just shoot him and be done with it. First, what if he escaped from captivity on the way through occupied Europe? Second, he has done nothing wrong. Being a grass isn't a crime. Third, Hogan and his men are the war criminals - they often engage in combat activities out of uniform. Williams is going to be acquitted.

Stupidity: Why would a cop bring up an old case when he knew he was the murderer? It makes no logical sense and only brought his downfall.
Suggested correction: He was being blackmailed by Gary Roberts. He "reopened" the case as a ruse to kill Roberts.

Mr. Monk and the Airplane - S1-E13
Stupidity: When the pilot asks Monk for some ID, who cannot provide it, and the flight attendant exposes Monk as the passenger that is causing her a lot of trouble, normally Sharona would step in in these type of situations to convince whoever with her voice of reason that Monk is indeed a famous detective and sought after consultant for the SFPD. Her silence in this situation and later when the flight attendant confiscates the lighter and takes the glass with the evidence residue is incredibly out of character. (00:30:40 - 00:32:30)

Stupidity: After eventually arriving at the stadium, why didn't Ash tell anyone that he was late due to getting kidnapped by Team Rocket? He arrived with half of his Pokémon exhausted and subsequently lost his battle. If he informed everyone about his situation, his battle with Ritchie would likely have been postponed until tomorrow, giving him some much-needed time to rest, which would have given him a bigger chance to win.

The Farting Sex Tourist - S1-E4
Stupidity: Joel finds prints in Serbian and is stressed because they'll never find someone to translate Serbian in Santa Clarita, goes to great lengths to interact with the principal's Serbian grandmother, etc. Google translate can understand Serbian just fine, but this doesn't even occur to him.
Suggested correction: Except the 16th century Serbian alphabet isn't available to most people to type into google translate. Plus the script used makes it difficult to distinguish which character is which sometimes even if you could find characters to cut and paste tediously into google translate.

Stupidity: After Cory and Shawn fish Mr. Feeny's watch from the septic tank, he suggests they jump into the lake to clean off. Cory protests, reasoning that it's only 20° outside, to which Feeny dismissively tells them to take a sweater. They then reluctantly abide. Someone of Feeny's education should know better than to allow them to jump into a freezing cold lake. They could both get hypothermia, and they're all currently isolated in the Pocono Mountains with no nearby medical facilities.

Free Family Portrait Studio - S8-E24
Stupidity: Dwight is seen walking out of the bathroom with the diaper in the direction of the main part of the office in which Angela sits. If he was to try to stay hidden (which was obviously the whole point), he would have gone through the exit of the annex, waited until she was distracted/or hide it for later and Angela never would have seen. This was done because the plot required for Angela to notice but Dwight could have easily kept it hidden. (00:10:40)

The Succubus (a.k.a. Chef's Mama) - S3-E3
Stupidity: When Kenny and Cartman are sitting on the bench, Cartman can't start the tape as he has fallen asleep. Kenny then tries to wake him up, but wouldn't it have made far more sense for him to just start it himself, as he is sitting right next to it? Cartman's job was to push the play button. It was not like he had to rewind, fast forward or even eject the tape, so all Kenny had to do was just simply push the play button and tape would have started to play.

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.

Long Night's Journey into Day - S5-E23
Stupidity: Rob tells Jerry "I haven't stopped sneezing long enough to take allergy pills" yet right after he says that, he doesn't sneeze anymore till he gives out his home address. He could have just taken his pills then. Someone behind the camera probably reminded him to continue sneezing. (00:16:52 - 00:18:00)
Suggested correction: He's exaggerating, but a character not taking a pill in this situation doesn't constitute a stupidly mistake (minor plot hole). I've been in situations where I needed to take an allergy or pain pill and didn't, even though I had a chance, because my mind or focus was somewhere else.

Turkey Guys - S13-E5
Stupidity: The whole episode revolves on the turkey that Peter ate. Lois sends him and Brian out to get another one. She stalls dinner the whole episode waiting for them to get back. Problem is the turkey is frozen! It will take at least 6 or 7 hours to cook and Lois acts like as soon as they return with it, it won't take long to to cook, so the stalling makes no sense. (00:12:45)

Snow White and the Seven Bradys - S5-E3
Stupidity: When the kids all pick the random-shuffled papers to choose which kid will be which dwarf, it NEVER occurred to them that with six kids and seven dwarfs they would be one short. This was only discovered once Peter (the last to pick one) was now up for a turn. How did nobody figure that out before the name-choosing even started?

Stupidity: When Trevor died, he saw himself on the floor therefore he was aware of what happened to him, but he was shocked to learn that his body was originally dumped in the lake by his friends.
Suggested correction: After Trevor died, the other ghosts took him to another room to explain to him what was happening, only Sasappis saw what happened to Trevor's body, and he kept it a secret to protect Trevor's image of his "bros."

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: Samantha could put a spell on Larry and Louise to stall for time. She could freeze them or make them uninterested in Jonathan until Clara remembers her spell.

Stupidity: The Kramden's door opens out towards the hallway. Yet anytime they need to block the door for protection, they put furniture up against it. That would serve no purpose, even with that cheap slide lock they have. The landlord or criminals could just open the door and push the furniture out of their way.

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)

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)
Suggested correction: Not true. The crime he committed was treason, a capital offence under both civil and military law at the time. Being a partisan is not an offence under the Geneva Convention, as these were mainly captured flyers, led by a small team of specialists. To execute a prisoner, as you suggest Hogan's men should do, is murder, also a capital offence at the time.
stiiggy
Nobody from Stalag 13 accompanies Williams back to London - so where is the evidence of his "crime"? Hogan and his men often take part in combat activities both out of uniform and even wearing German uniforms, which is itself a one way ticket to a firing squad.