Things I've Noticed Watching for the Nth Time
The yellow Partridges were made much more vivid yellow starting in the second season. When the Partridges are facing the left side of the screen (left as you're looking at it), their eyes are closed. The first time Mama Partridge turns her head, eye on the other side is still closed. Second time it's open. As the little Partridges turn their heads, eye on the other side is open.
The exact same performances were reused. For instance, "Summer Days" in "Dr. Jekyll and Mr. Partridge" is the exact same footage as in "Home is Where the Heart Was." Incidentally, I consider this the single cutest thing in the whole series, particularly the exchange between Keith and Tracy, made poignant now that they're both gone.