In the episode Fred thought Wilma’s mother was coming to move in and he decides to build her a house, it turns out mom meant she was moving in with Wilma’s sister and her husband. Was this the only time the sister is mentioned?

Hmmm I wonder!

Fraternal twin Sisters Mica and Micky, and a Brother Jerry .Apparently they were introduced in the spinoff show, The Flintstone kids per Google.

Fraternal twin Sisters Mica and Micky, and a Brother Jerry .Apparently they were introduced in the spinoff show, The Flintstone kids per Google.

Then I guess I was right. That was the only mention in the original series, as part of a comedic misunderstanding to explain the mix up in thinking Wilma’s mother was moving in.