Big Bang Theory ran on CBS for 12 reasons. The sitcom centred around the lives of five characters, Sheldon, Leonard, Raj, Howard, and Penny, with two additional main characters added in the later seasons, Bernadette and Amy, along with several other supporting characters and guest appearances.
Despite the intricate geek-speak on the show, since the friends were all science nerds working in physics, engineering, neuroscience, and other similar areas at Caltech University, fans loved the show, making it one of the most popular on television.
One exception was Penny, who was a waitress and aspiring actress turned pharmaceutical salesperson who wasn’t into Star Trek, Star Wars, and science like the others. But she was central to the story nonetheless. Yet strangely, Penny never had a last name. Why was that?
Many theories have floated around the Internet, especially since, even in the final episode, her surname was never revealed. Here’s a look at 5 of the most outrageous theories, and 5 truths about why we never found out.
10 Penny Was A Spy: Theory
One of the most outlandish theories suggests that Penny was actually a spy, sent to keep an eye on Sheldon and Leonard. It could make sense, given that they were both working on pretty important research that might interest the government. Indeed, at one point, they did find themselves recruited by the government for a project.
Some theorists even go so far as to say that this is why Penny steals their Internet. It isn’t because she can’t afford her own, but because it makes it easier for her to spy on them. This is just way too far-fetched for a sitcom, though.
9 It Wasn’t Intentional: Truth
The show had aired a number of episodes already, during which time we learned of the surnames of all other major characters, including Sheldon (Cooper), Leonard (Hofstadter), Raj (Koothrappali), and Howard (Wolowitz). Yet we had no idea what Penny’s last name was. In fact, on the IMDb page for the series, it simply shows “Penny” as though she was a minor character, even though she’s listed third on the billing.
Even Bernadette (Rostenkowski) and Amy (Farrah Fowler), who joined the cast later in the series, have surnames, as do supporting characters like Stuart (Bloom) and Bert (Kibbler). But the truth is that it wasn’t intentional to leave out a surname for Penny. It just sort of happened.
8 Penny Was a Stage Name: Theory
Penny did move to California with hopes of becoming an actress. So one theory suggests that not only do we not know her surname, but Penny wasn’t even her real first name. Rather, it was a stage name she adopted in order to get more acting jobs.
It would stand to reason, then, that if Penny wasn’t even her birth name, why would we even need to know her surname? If anything, we’d want to know her real given name. Of course, there’s no truth to this outlandish theory.
7 Producers Got Superstitious: Truth
After the show had been running for a while, producers realized they had never mentioned Penny’s last name. It wasn’t intentional, it just was never discussed and never ended up being written anywhere into the script. And after that, they became superstitious about revealing it.
“We got nervous and superstitious and giving her [a last name],” confirmed executive producer Steve Molaro at the Wondercon panel this past March. It really is as simple as that, though slightly troubling that there was reason to reveal the surnames of the other characters. It could also be that they worked in a formal educational system were many colleagues referred to them as Mr. Cooper or Mr. Wolowitz, whereas Penny, in the beginning, was a waitress who was only ever referred to by others using her first name.
6 It’s Johnson: Theory
Some fans in online forums swear that her last name was Johnson because it was revealed at one point that she married Zack Johnson in Las Vegas, not believing that it was real. If this was the case, then legally, her name would be Johnson, right?
Well, not really. Even if she did marry him, unless she actually filled out official name change documents, her surname would have remained the same. That said, others note that Johnson is the most common surname in Nebraska, where she’s from. So it’s entirely possible that Johnson was her last name anyway, before she even married Zack. But probably not.
5 It's Hofstadter: Truth
OK, so we technically don’t know if Penny ever had her surname legally changed to Hofstadter after marrying Leonard, which isn’t a requirement. These are the types of mundane details that aren’t necessary to show in a sitcom. Though it would have presented a great opportunity to reveal her maiden name.
Nonetheless, at the Wondercon panel in March, executive producer Steve Molaro confirmed that Penny’s last name “will always be Hofstadter.” Some have criticized this notion, saying it implies that Penny didn’t have an identity until marrying Leonard. But the truth is that she was Penny, and that’s her identity. She doesn’t need a last name to confirm it.
4 It’s Longbottom: Theory
In addition to speculation about Johnston, some others report believing that the name was Longbottom. Yet there’s no reference to prove this and it seems to be nothing more than Internet lore.
The theory is that this name was indicated on episode transcripts, which someone, somehow got wind of and “leaked” the details. But again, this hasn’t been substantiated, so really, it could have been anything written on those early transcripts. Only a select few people actually know the truth.
3 Kaley Cuoco Doesn’t Want to Reveal It: Truth
Kaley Cuoco, the actor who played Penny for all 12 seasons, says she doesn’t really want to ever reveal what Penny’s last name was. “It’s kind of a personal thing,” she told CBS News in 2017. “It feels like a jinx. We haven’t said it for so long. I feel like if we said it, the world would explode.”
This implies that Cuoco knows what Penny’s last name is supposed to be, presumably having seen it in the original scripts. Either way, it sounds like fans will never find out.
2 She Doesn’t Have A Last Name: Theory
Like Cher or Madonna, some suggest that Penny simply doesn’t have a last name. Of course both Cher and Madonna, and every other one-named artist, actually have surnames. So this is one of the sillier of the many theories.
And in actuality, this “theory” was first presented by Kaley Cuoco herself, meant to be in jest. This was her response one time when asked about the mysterious missing name. The truth is that Penny did have a last name, as anyone would.
1 Kaley Cuoco Was More Concerned About the Elevator: Truth
While Kaley Cuoco, who plays Penny, seemed fine with the character’s surname never being revealed, as she noted in interviews prior to the final episode airing, there was one thing she did want to get resolved before the series came to a close: that darn elevator that was always out of service in the building.
She got her wish, as in the final episode, the elevator was finally fixed, much to the shock and awe of Sheldon, who rode in it with Penny for what seemed like the first time. The running joke throughout the series is that the elevator was always out of service, leaving the gang to trudge up several flights of stairs to their apartments. The time they spent walking, however, was when many important conversations took place.