This is the sort of thing that warms the heart of sitcom buffs and probably drives everyone else crazy: someone gathered all the Petticoat Junction introductions together in one video, to show how a sitcom intro developed through multiple cast changes, the switch from black-and-white to colour, and the final collapse into a show where hardly any of the original cast is left. I wish someone would do this for One Day at a Time (all the intros are online, but not grouped together in one video like this). As someone has noted, this is one of the reasons why many shows today avoid elaborate intros with the characters in them: when actors leave, or new characters are added, you don’t have to go out and reshoot everything.