The Flintstones debuted in 1960. The series went through a lot of preliminary development. For example, the titular family was originally the Flagstones. In this selection from an early pilot episode, we can see Fred, Wilma, Barney, and Betty. But they all, except for Wilma, look different from their later form. Fred in particular looks more like a caveman and is voiced by a different actor.
-via Between the Pages