There's No Place Like Home (2) - S5-E6
Other mistake: At the very end, Mr. Hanson is seen walking toward the church. Because of his stroke, he's slow and unsteady. We see several close-ups of his feet, showing how he's struggling. Two of those shots are the same footage. It's obvious, because you see that he drags his foot over a small stick in the road and stumbles - and in both shots, it is exactly the same.
Welcome To Olesonville - S9-E3
Continuity mistake: Mrs Olsen cleans up the old Hansen house to sell, however it was made the blind school years back and burned down, killing Mary's baby and Alice Garvey.
Laura: I hate that Nellie Oleson.
Caroline: Laura! Don't say "hate" - don't even think "hate"! I'm sure Nellie has her good qualities somewhere.
Charles: Your ma's right, half-pint. Now on the way home, we'll try and think of some.
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.