The Wolves - S4-E5
Character mistake: At one point upstairs (after Mary tells Laura to turn off the lights), Laura tells Mary she's using the moon to see her book - and even the moon itself is shown afterwards. However, this would not be realistically possible as this window looking outside faces north and the moon (as well as the sun) would never shine into that side of the house as neither is ever on the north side of the sky, especially in Minnesota.
Times Are Changing (1) - S9-E1
Character mistake: Almanzo says he hasn't seen his brother Royal in 10 years, but in fact he saw him not long ago as he looked after his 2 sons who were terrors, and at that time Royal didn't even have a daughter.
Suggested correction: Royal's wife was pregnant when he visited years before Laura had the baby.
What happened to Pearly Day? Almonzo's younger brother?
Not sure if this varied in the show, but in real life Pearly Day had six children and died in 1934 just a month prior to his 65th birthday.
Almanzo had 2 brothers. Royal and Jenny's dad, the one that was dying.
That may not work, unless Laura and Almonzo were not married yet at the time of Royal's first visit, but it is a good suggestion.
In the TV series, the episode that they were taking care of the boys was only six episodes before Laura found out she was pregnant, and Nellie's babies were still babies throughout that time so it wasn't that long. And Rose wasn't that big When they came to visit, so it was probably only 1 1/2-2 years of a time gap. Also, when Royal and Jenny came to visit, Almanzo introduced Royal to Laura as if they had never met before.
It was NOT years! Royal, his wife and 2 sons visited Almanzo in Season 7. His wife did announce she was pregnant in the end. However, when Royal comes back to visit with Jenny, at the beginning of Season 9. If Jenny is supposed to be the baby Royal's wife was pregnant with then she would have still been a year old or 2 at most. They do explain that his wife died, but what about those boys? They would have been early teens by then. Nothing is ever said about them or why they aren't with Royal.
But Laura says "glad to finally meet you Royal", when he came with Jenny. But she met him when he came with the boys.
Albert Quinn Ingalls: Ma, please don't tell me I'm too young to know how I feel.
Caroline: I wasn't going to tell you that, and don't ever raise your voice to me while you live in this house.
The Voice of Tinker Jones - S1-E11
Trivia: Sean Penn is in this episode, albeit with no lines, always wearing the same blue shirt. His father directed this episode.