The Big Bang Theory may have wrapped up almost a full year ago but that does not necessarily mean all their loose ends have been tied up. Kaley Cuoco's Penny is at the center of one of those biggest loose ends of all: her last name, or rather, her lack of one.
While the show ended with the character's official name as Penny Hofstadter, fans have never been given the satisfaction of knowing what her last name was before her marriage to Leonard. With every major and prominent recurring character having full-fledged full names (ex. Sheldon Cooper, Rajesh Koothrappali, Howard Wolowitz, Bernadette Rostenkowski-Wolowitz and Amy Farrah Fowler), it just never felt right that Penny was never given more than a simple "Penny".
Despite being a member of the main cast right from the beginning, Penny's backstory arguably took the longest to progress. Penny's father, Wyatt, is only just introduced in Season 4 as a catalyst for approving of Leonard since he was relieved to see his daughter dating someone academic. On the other hand, Penny's mother had appeared on the show in the form of speaking to Penny off-screen on the phone, she surprisingly appeared for the first time in person seven years after Penny's father in Season 10. Played by Katey Sagal, who previously portrayed the mother of Cuoco in 8 Simple Rules, Penny's mother Susan makes her debut into the series when she goes to California for Leonard and Penny's wedding redo. With some semblance of her family-life finally established, fans were eager to know if her last name would also be established. However, neither her father's last name nor her mother's maiden name is ever mentioned.
One key theory that supports why Penny lacks a surname despite all other major players having one is the fact that her character was only added to the show after the pilot was rewritten. Before Penny, there was Katie. Katie was meant to be the girl-next-door to Leonard and Sheldon but, unlike Penny, this version of the girl-next-door was more mature, assertive and overtly sexy rather than sweet. It is highly presumable that during the hectic rewrite from Katie to Penny, Chuck Lorre simply forgot to give Penny a surname. There is potential that Lorre was not initially confident that Penny would be a keeper and may have not wanted to give the character too much backstory, such as a conspicuous last name, in case another rewrite needed to happen. After it became clear that Penny was going to be part of the show for the long haul, it was too late for the character to naturally introduce herself with a surname obligatorily attached.
It would have been rewarding to finally get the long-awaited reveal of Penny's last name after years of mystery but a shoehorned last name unveiling, just for the sake of satisfying curiosities, would have been too gratuitous and therefore disingenuous. For such a principle character that had grown to become so beloved, it would ultimately have been a disservice to give her a last name that did not suit her after all these years of build-up.
In this case, fans are likely better off letting the mystery live on and enjoying the endless possibilities that go along with continued speculation since the answer may not live up to what they hope for. One thing is for sure, Penny herself is happy to end the series as Mrs. Penny Hofstadter.
Premiering on CBS in September 2007, The Big Bang Theory followed four scientist friends that befriended a young woman living in their apartment building as they balanced their careers and love lives with plenty of geeky references and pursuits. The series concluded with its 12th season last May.