Question: What was the name of the redhead woman with the kilt on, with Wille? (She only appeared once).
Corrected entry: This is for the Season 17 episode 'Marge's Son Poisoning'. Principal Skinner says that he and his mother have been doing karaoke together since he was in the 4th grade, but in the Season 9 episode 'The Principal and the Pauper', it was revealed that the 'Seymour Skinner' we know is an impostor, a man who assumed his army sergeant's identity after he was killed in combat.
Correction: Skinner (or Armin Tamzarian, if you want to be totally truthful) has been telling lots of stories about his childhood with Mrs. Skinner. It doesn't mean that the stories are true, but he tells them to gain credibility for his role as Seymour Skinner.
True. Even in the episode "The Principal and the Pauper", the judge told everyone to forget anything happened.
Question: Who will teach Bart's class after Mrs. Krabappel's passing?
There was an episode in which Ned went to Springfield elementary as a substitute but left. Bart convinced him to come back. Then in S30s finale, "crystal blue haired persuasion", Flanders show Marge a test that Bart got in "his" class, suggesting he is the new teacher. However, Simpsons wiki fandom shows that it a is a temporary job.

Revealing mistake: When Homer pushes the soda vending machine next to the candy vending machine, a large scratch appears near the upper right corner of the screen.
Suggested correction: This is in the questions as well. With the long amount of time the artists have to make an episode it's very hard that something like this would get by them. It's probably the device you watched it on.
Lisa's Pony - S3-E8
Corrected entry: When Homer falls asleep in the car, he hits the dashboard with his fist, and the airbag pops out. If you watch in slow motion though, he doesn't hit anything at all. (00:19:30)
Warrin' Priests Part 2 - S31-E20
Question: Is there a reason Bart was so conspicuously absent from these two episodes? Homer even asks where he's been.
Answer: He was probably irrelevant to the plot so he was not included.
It's called lampshade hanging. By drawing our attention to it the producers are letting us know they are aware it is an issue.
Yes, but even when the family is having dinner together, he's not there.
Corrected entry: When Lisa mocks Bart in French, she sings, "Vous êtes Baby Stinkbreath." However, "Vous êtes" is the formal construction. A person would not use this when speaking to his or her brother, especially when deliberately being disrespectful towards him. "Tu es," the informal form, would be more appropriate.
Correction: Lisa may still be learning, and it's an easy mistake to make.
Oh, Brother, Where Are Thou? - S2-E15
Question: How exactly did the production of Homer's car bankrupt Herb? If Herb, as a highly successful car manufacturer, was spending so much money spoiling Marge and the kids that an $82,000 price tag for making a car was enough of a straw to break the camel's back, wouldn't he have gone bankrupt sooner than later anyway?
Answer: It wasn't the cost of one car, but that they'd produced thousands of Homer's ridiculous vehicles, which they'd marketed as a family car, but cost five times as much as a new car at the time. No one would buy them and the company went under.
Wasn't the car just a demo though? How would they have been able to produce thousands of cars in such a short amount of time?
Big difference between a "demo" or prototype car compared to a launch car. The dealers must have stock available of the launch car so people can actually buy them straight away.
Question: How can Flanders afford stuff like a huge boat and a motorhome if he doesn't make a lot of money?
Answer: From time to time he has explained his above average income has come from a variety of reasons. First of all he has mentioned from time to time of other business ventures he has been involved. At one time he was doing advertisements when he shaved his moustache and another he was trading in religious website store. Secondly the Leftorium that he runs has had his highs and lows which would explain why he can sometimes afford more expensive items. Thirdly he seems to be quite clever when it comes to saving and business. For example he showed Homer about the Mega Savers course that showed about how to buy more expensive items at lower prices.
And he was once a successful pharmacist. He says so when he burns his tie announcing the Leftorium.
Burns Verkaufen der Kraftwerk - S3-E11
Continuity mistake: Before Horst wants to talk with Homer, Lenny is standing beside the donut box, who wasn't seen in the shots before and after. (00:12:15)
Continuity mistake: At the beginning, when the bus is driving to the school, the streetlights outside disappear/reappear between shots. (00:01:30 - 00:02:20)
Other mistake: When The Town is singing the Christmas carol you can see Sideshow Bob, who was arrested and jailed in series 1. We know he hasn't been released, as that's a plot point over the show. (00:18:10)
Suggested correction: Maybe he was allowed to participate due to good behavior. That's a possibility.
Good behavior or not, a prison wouldn't furlough an inmate just so they could participate in a snow day.
I'm not sure if it's been discussed here or listed as a mistake. Part of the problem with "The Simpsons" and the Sideshow Bob character is that time both moves forward and doesn't move. In "A Brother From Another Series," Krusty visits the prison and tells Bob he hasn't seen him in years because Bob had been in prison all those years for his crimes. Yet Bart and Lisa are still the same age and in the same grade. Bob is also let out of prison on a work-release program in the episode.
Character mistake: Burkina Faso is listed as being among the Southern Hemisphere locations Bart called when Homer is looking over the phone bill; since Burkina Faso is completely within the Northern Hemisphere, it would have made no sense for Bart to call there.
Suggested correction: It may not make sense, but Bart isn't exactly the sharpest tool in the shed. In this same episode, he looked at his globe and thought Rand McNally was a country and was convinced by Lisa that the citizens there wear hats on their feet and that hamburgers eat people. Additionally, he could have just decided to prank call someone there if for no other reason than he thought the name of the country was funny.
Entirely possible, but since Bart had a globe right there to refer to, even someone with his limited geographical knowledge would have been able to tell that Burkina Faso is in the Northern hemisphere, unlike the other locations he did call as depicted in the montage (Antarctica, Argentina, unspecified South American nation, etc).
Corrected entry: In the scene where Homer is in the bathroom, Marge yells to Homer for breakfast. We see him running naked without a towel but by the time Homer, Bart, and Lisa get to the breakfast table, Homer is wearing his usual shirt and trousers.
Corrected entry: Homer shoots the TV on, and talks to the other members, then when you next see a shot of the TV screen, it has turned off. And it can't have broke because other bullet holes can be seen too which didn't break it.
Corrected entry: Apu is seen at Homer's BBQ shoveling meat into his mouth, yet, just a few minutes later, he explains to Lisa that he is a "strict vegetarian."
Corrected entry: When Bart is crossing off the days in his calendar to show how long he has to go without seeing the no-good Jessica, he eventually circles the first day, a Monday, saying, "OK, day one," and then sits to wait. Immediately after, Marge sticks her head in the door announcing it's time for church - which is usually on Sunday.
Corrected entry: In the beginning of the episode, the family goes to the Googolplex theater but when the show cuts to a shot of the movie screen when Bart and Lisa are watching Space Mutants, the decor around the screen indicates that they are at the Aztec theater. (00:03:20)
Correction: Seeing how Springfield used the same plans for Springfield Elementary and North Springfield Elementary it should be no surprise that two theaters in Springfield have the same decor.
They could have been owned by the same company at one time or changed owners. This is also a running gag on the show such as what's on the other side of The Simpsons' house?
Corrected entry: Nelson Mutz is one of the person banned for life by the comic book seller. If so, why he is seen later during Tom Savini's presentation?
Corrected entry: Bart asks Lisa how she knows so much about the Talmud. She credits her imaginary Jewish friend. But Bart was with Lisa in episode 3-6: "Like Father, Like Clown," when she made an extensive study of ancient Jewish texts. So Bart shouldn't need to ask the question in the first place, and Lisa's answer is incorrect, or at least incomplete.
Answer: She has no name and was the Female Groundskeeper at the Shelbyville Elementary School in the episode "Lemon of Troy". She was basically a female version of Willie, even down to having the same type of insults: "Slow down, ya sidewalk-surfin' cube gleamers!"
I don't think that's who the submission was referring to. There was a different woman who looked nothing like Willie.