Susan

This unnamed woman is the mother of Penny as well as a man and another woman and the wife of Wyatt. She lives with her husband in Omaha, Nebraska on their small farm where they raised their three children.

She is the only mother of any members of the gang who has never been seen on the show.

In The Flaming Spittoon Acquisition, Sheldon implies that she's fat and Penny reveals that her mother smoked pot when she was pregnant with her.