In episode 26 where the castaways form an orchestra, Mary Ann is upset because she doesn't have any musical talent. Gilligan shows her how to play a musical saw. She shows her gratitude by kissing him, and we hear another "boiiiing!" which clearly does not come from the saw.
When the Professor refuses to join the others in what he sees as a ridiculous escape plan involving a magic stone that grants wishes, Mary Ann declares she won't leave without him. Mrs. Howell protests, "You can't stay with him, it's not proper! Thurston, they need a chaperone!"
A fan once pointed out to Russell Johnson that if the show were filmed today, the castaways would all be living in one hut. They actually started out with one communal hut, and an early episode centered around the girls demanding their own hut ("We've simply got to have some privacy!"). When the men fail to see this as a priority, Mrs. Howell tells Ginger and Mary Ann the story of Lysistrata (as in, the inventor of the Lysistrata Gambit).
Mrs. Howell: She persuaded all the women in her town (grins at her husband) to ignore the men completely [emphasis hers] unless they got what they wanted.
Ginger: Well, I think we should all act like Lysistrata.