Nellie is seen sitting on the front porch embroidering the alphabets as she waits for Jason and Laura to walk by. In season 7 Sylvia part 1, Caroline is sitting in the rocker talking to Charles, embroidering the same cloth.
First appearance of Willie's infamous "stand in the corner" routine.
The phonograph was invented in 1877. Laura Ingalls would have been 10 years old.
During the (secretly) recorded conversation with Nellie, Laura says "I'll never be as smart as he is. But I can work awful hard at it." But later, when Nellie plays the recording of their conversation, the first sentence is now "I'll never be as smart as Jason."
Both Eric Shea (Jason) and Melissa Sue Anderson (Mary) appeared previously in separate episodes of The Brady Bunch (1969-1974), playing friends of Bobby's.