When Harriet Oleson first answers the telephone and screams "Walnut Grove" into it, this was improvised entirely by Katherine MacGregor.
When Nellie is playing the piano toward the end, she's playing a slightly wobbly and off-key version of the Little House theme.
Royal Dano also played Sylvia's father in "Sylvia"
Mrs Oleson gets on Alice's case about lying to Jonathan about her first husband, but in "The Preacher Takes A Wife", she lied to Nels about being engaged to another preacher before she met Nels, she never told him either. Again, this shows what a self righteous hypocrite Harriet Oleson is.