The Mysterious Affair at Styles - S3-E1
Plot hole: Can't fault this massive plot hole to the adaptation, but to the source material; the culprit (forgetting the stupidity of writing an incriminating letter detailing the plan to murder someone, and put it in a desk he shares with her) since there are people outside the room that are about to enter, tears the letter in 3 neat vertical strips, rolls them, puts them in the vase on the mantlepiece, and then opens the side door to slip away...instead of simply pocketing the letter and going through that same door. Nobody was going to search him or anything and could have burned it, torn it into confetti, anything, later. It takes way way longer to do what he did, which needed him to stay there in the room increasing the chances of being found out. And of course he and his accomplice do not retrieve the letter after.
Plot hole: The Winslows' younger daughter, Judy, disappeared from the show in 1993 (halfway through the series' run) with no explanation.
E-I-E-I-(Annoyed Grunt) - S11-E5
Plot hole: When the Simpsons run away from the duel, they go to Homer's childhood farmhouse. But Homer and Grandpa burned the farmhouse down in the episode "Grandpa vs. Sexual Inadequacy".
Robo Koopa - S1-E52
Plot hole: Near the end, Robo Koopa sets down Dr. Nerdnik after he had just captured and held him hostage. Why would he do that? (00:11:55)
Plot hole: The Triforce of Wisdom is kept in Link's room up in a tower. It does seem logical to keep it with Hyrule's greatest hero to keep safe, but that's all you ever see protecting it. Hyrule is a large kingdom, and the Triforce of Wisdom is a vital part of keeping their community safe. Yet the only one protecting it is Link. And he's not with it 24/7. The room is not very secure either and is breached all the time by Ganon's forces. A kingdom like this would have knights to post all around the tower and be in Link's room when he's away. But nope, not here. (00:01:10)
Another Mother - September 30, 1981 - S2-E13
Plot hole: Sam wallops both kidnappers and rescues the son. They then leave the two child molesters unconscious beside their van. No one calls the police or has them arrested, so they're free to kidnap another kid. Sam doesn't leap until after an epilogue in which the loose ends are supposed to be resolved - but this question is left unanswered. It's not excused by a "just because we didn't see it happen doesn't mean it didn't" defense. The viewers shouldn't be left with a dangling plot hole, and one line could have cured this one.
Rent-a-Pop - S2-E7
Plot hole: After the meeting with Zack's "fake Dad", Mr. Belding informs Zack he wrote a letter to see the Dad again... However when the "real" Dad sees the fake "Belding" (whom the Dad didn't know was fake), the Dad never questioned about the "seeing him AGAIN" letter when this real Dad never met Belding before. In addition, wouldn't the Dad question this letter to Zack anyway?
Plot hole: If the electrical lights go out at a quarter past ten at Guardbridge, how come there is bright electrical (as suggested by it not flickering like candle light) light coming from a room behind Hal Stanton and Catherine Faulkner when they kiss? This scene takes place after 22:15.
Sukeban no me ni namida? Rûru muyou no kakutou shintaisou kecchaku - S1-E13
Plot hole: In the anime, Ranma commits an unsanctioned violation of the rules when she throws Kodachi out of the ring (the time when she gets saved from her schoolmates); she in fact grabs Kodachi's arms using legs and feet, and projects her. In the original manga there is no such mistake; Ranma used her feet to spin the club Kodachi was holding, so was not throwing Kodachi directly, but using the tool just as the rules say. (00:15:45)
Plot hole: When Ellie leaves Ft. Smith on a whiskey boat, she's just been seen with the morning sickness a day or two before. When she leaves the whiskey boat, somewhere between Arkansas and Nebraska, she says she's pregnant but is not showing at all. Even the snaggle-toothed frontier weirdo played by Steve Buscemi remarks that, "You ain't gonna be havin' no baby fer a while yet." The day she gets to Clara's, near Ogallala, Nebraska, she has the baby. Pregnancy lasts nine months. Morning sickness usually begins at about six weeks into it. Ft. Smith, Arkansas, to Ogallala is 561 miles. Even just walking three miles an hour for eight hours a day, one could make it in less than a month. But going via boat and mule-drawn wagon took her over seven months?
The Assassin - S6-E8
Plot hole: There's no way Shelley Hack could clean up all that mess of blood and three dead assassins with only an hour or so before her dinner party.