Reason For Half Mast
If you notice during the opening of the series, you might have seen the American flags right on the half of the pole. The real reason is because before the filming began, JFK was assassinated. They finished the filming of the pilot episode on November 22, 1963 which was exactly the day President John F. Kennedy was shot.
Inside Joke
Back then, while the show was running, Newton Minow was the head of the Federal Communications Commission (FCC). Sherwood Schwartz, the creator of Gilligan’s Island (and The Brady Bunch), disliked him. So, if you can remember, the wrecked ship was called S.S. Minnow. Perhaps Newton didn’t notice.