Always a Godmother, Never a God - S6-E4
Stupidity: Rory arrives in Star's Hollow for the baptism. She parks presumably near the church. When she gets out of the car, she does not have a purse or car keys in hand. She apparently left the car unlocked and left the keys in it. It's just plain dumb.
Stupidity: Aunt Bee learns that a New York writer and his wife have moved to Mayberry and she invites him to speak at a Literary Club meeting which will be held at her home. By telephone, Aunt Bee gives directions to the writer's wife. She says, "We're a quarter mile outside of town" - but she neglects to say in which direction.
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.
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: 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.
Stupidity: When an officer is speaking to who he thinks is colonel Tuttle but is really Radar with a surgical mask, he says what he needs to and is about to leave. Radar who was alone at the time and was completely in on the fact that Tuttle never existed, could have kept up the façade and let him leave, but instead chooses to reveal himself which was utterly pointless.
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.