Deliberate mistake: The house is in a field with no lights around it and should be dark at night, but during exterior shots at night, the house is always lit up on the outside and the interior shots always show very bright lights coming into every window (much brighter than when shown from the outside). There would not be lights that bright shining into the house during that time period. Obviously, just an effect so viewers can physically see the house and characters talking.
Little House on the Prairie (1974)
1 deliberate mistake in show generally - chronological order
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.
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.
Trivia: Peter Billingsley of "A Christmas Story" plays Gideon in this episode. This was his television debut at age 11.