The Suit
Whenever Barney would go out on a date or any formal affair, he’d wear a white straw boater, salt and pepper-pattern coat, and a red bow tie. After he left the show and began his movie career, Don Knotts almost all of the time wore the same suit. You can see it in films like The Ghost and Mr. Chicken, The Reluctant Astronaut, The Incredible Mr. Limpet, and How to Frame a Figg.
Opie?
Not once in the show do they say what happened to Opie’s mother. All we know is that Opie was just “a speck of a boy” when she passed. We don’t know her first name, we never see a picture, and there is no grave that we know of.