In the Big Bang Theory, one of the main characters is "Penny". In the 12 seasons, does it get mentioned what's Penny's full name before she married to Leonard Hofstadter?
She didn't have one.
It is never mentioned before she became Hofstadter.
Penny is the only main character of the program whose last name was not revealed, although she has been occasionally referred to or addressed with the last name Hofstadter since her wedding.