When Harold pours the drink for himself, he just puts a splash in the glass, but when he raised it to drink the shot glass is full.
Johnathan tells Charles that they are near Minneapolis so they can visit Alice's mother. Mankato isn't that much closer to Minneapolis than Walnut Grove. It's 95 miles away. In a wagon it would take them most of the day if not more to travel that distance.
Charles and Jonathan went from Northfield into Minneapolis - roughly a distance of 43 miles.
When Caroline and Alice approach the Garvey home with the new telephone pole not showing installation with turned up earth does show when Johnathan pushes it over.
At 18:28, Albert calls Mrs. Olson Miss Oleson.
Charles asks Jonathan how many years he's been married, and Jonathan replies, 'I don't know. 15 maybe 16.' The Garveys celebrated their 15th anniversary over a year ago in the season 5 episode Harriet's Happenings. If Jonathan remembered his 15th anniversary a year prior, he should know he's been married 16 years now.