Hanna-Barbera created two live action "wrap-around" shows for Saturday Morning. Basically, they were costumed characters engaged in skits and music who introduced various cartoon shorts.
The first, on NBC in 1968, the iconic "Banana Splits Adventure Hour" (with characters created by Sid and Marty Krofft) included a live-action serial called "Danger Island." Remember "UH-OH CHONGO" or words to that effect? These very colorful and well-made episodes starred Jan Michael Vincent and were directed by Richard Donner who would go on to help "Superman: The Movie", "The Omen", and the "Lethal Weapon" franchise.
Nine years later, "The Skatebirds" premiered on CBS. Less revered than its predecessor, these roller fowls introduced the live action "Mystery Island." You think they could have come up with something a little different. Well, there was a little more sci-fi to compete with the Filmation live-action kidvid at the time.