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.
Home Again - S9-E16
Character mistake: Mrs. Oleson, talking to Willie, tells "Albert" to go clean up his room while Mr. and Mrs. Oleson, Willie, and Albert are talking in the Mercantile. (00:39:20)
Character mistake: When Eric is asked to spell repetitious at the spelling bee he spells it R E P I T I T I O U S... Alice Garvey says "correct" but it was incorrectly spelled.