What is the first name of Penny's father?

Penny's father's first name is Wyatt.

Penny's father is Wyatt, portrayed by Keith Carradine in The Big Bang Theory. He is a farmer from Nebraska who is protective of Penny and initially takes a strong interest in her relationship with Leonard.

Wyatt first becomes important when Penny explains that he tried to raise her like a boy, a detail that helps explain some of her complicated feelings about her family. He later meets Leonard and quietly encourages him not to give up on Penny after their breakup. Wyatt also attends Penny and Leonard's wedding.

There is an early continuity wrinkle: when Penny first mentions her father in “The Maternal Capacitance,” she calls him “Bob.” The series later changes the established name to Wyatt, which is the canonical answer used for the character in subsequent appearances and reference material.