Wyatt
From The Big Bang Theory Wiki
According to the press release from CBS before the episode taped, Wyatt is the name of Penny's father. In a previous episode, however, Penny's father's name was given as Bob. Fan speculation before the episode aired was that Wyatt was either Penny's father's nickname, that it was his given name and that Bob was his nickname, or that Wyatt was in fact Penny's long-unmentioned last name.
