Kaley Cuoco’s Penny was undeniably one of the most lovable characters on The Big Bang Theory, but the bubbly blonde aspiring-actress-turned-waitress-turned-pharmaceutical-sales-rep had some mystery to her. Despite knowing the full names of the show’s the main characters — like Jim Parson’s Sheldon Lee Cooper and Johnny Galecki’s Leonard Leakey Hofstadter — and meeting all of Penny’s other family members (save for a sister mentioned early on in the show that somehow vanished from existence later on), viewers never learned Penny’s maiden name. In fact, her last name still remains unknown — even after The Big Bang Theory ended in May 2019.

Fans held out hope that they would get to learn it at various occasions throughout the series, including at her wedding — both the first and the second versions, the latter of which saw her family came out to visit for the first time — and even on the show’s finale. But somehow, it never came out. What we do know is that Penny took Leonard’s last name, Hofstadter after they tied the knot, so at least the show ended with her being Penny Hofstadter. Her maiden name, however, is a mystery.

After years of people begging for the big reveal, it’s been made clear that this wasn’t simply an oversight. With all the hype surrounding Penny’s last name, the Big Bang Theory producers made an executive decision that her surname was going to have to remain an unsolved mystery that could keep fans up at night.

Not revealing Penny’s last name is a superstition thing

It’s been reported that Chuck Lorre, the brain behind The Big Bang Theory, once hinted that Penny’s last name might be Barrington, but since there was never any confirmation of that on the show or behind the scenes, it would appear he was perhaps only teasing fans with a potential reveal. The Big Bang Theory executive producer Steve Molaro ultimately explained that after so much time without a last name for the girl next door from Nebraska, the creative team decided she didn’t need one – mostly because they were “nervous and superstitious about giving her” one. Molaro added that Penny’s last name “will always be Hofstadter” through her marriage, with her maiden name never coming to light.

With so much pressure from the fans, it’s possible that the Big Bang Theory team felt that no surname they could possibly give Penny was ever going to live up to the hype surrounding it. Another argument could be made that by the time fans started to notice that she was partially nameless, there didn’t seem to be a natural way to reveal her last name. Although fans were hoping to hear it at her and Leonard’s wedding, producers decided instead to leave it out yet again, and the same happened on the show’s finale when each of the main characters was called by their full names at the Nobel Prize ceremony.

Kaley Cuoco’s thoughts on The Big Bang Theory keeping Penny’s last name a secret

Over the years as the mystery grew for fans, Penny actress Kaley Cuoco went back and forth on the issue of her character’s last-nameless status. In 2017, she said that she herself didn’t really want to know her character’s secret last name: “It’s kind of a personal thing. It feels like a jinx. We haven’t said it for so long. I feel like if we said it, the world will explode,” she told CBS.

Cuoco did, however, add that she “has an idea” about what it might be — before clamping down and refusing to share that secret. Whether or not her “idea” was based on Lorre’s previous suggestion of Barrington was never confirmed.

In 2018, Cuoco backtracked a little, admitting she would like to know Penny’s last name. Then, at the wrap party for the series finale in May 2019, she again changed track. “I kind of love it,” the actress stated of the mystery. “So many things are revealed in the last few episodes; you get a lot of satisfying moments. But I kind of love that [we’ll never know her last name].”

The omission of Penny’s last name was initially accidental

While the lack of a last name became a conscious decision as the show progressed, the omission might not have been intentional at the outset. According to Newsweek, the character of Penny was rewritten at the last minute to replace another character, Katie, who was supposed to be the girl living across the hall from the two main leads. Test audiences apparently hated Katie, with her personality considered to be far too brash and sexual for the show. As a result, Big Bang Theory writers started from scratch with what would eventually turn out to be Penny, and called Cuoco, who had read for the original part, back to audition for the new character.

In writing the girl next door into the series so late in the production of the show, the writers and creators could easily have forgotten to give her a last name before The Big Bang Theory aired its first few episodes. When fans started to ask questions about Penny’s last name, the decision was made that it would be too conspicuous to add one in at that late stage, and thus she was left without a last name until she married Leonard and became Penny Hofstadter. And, like Molaro said, that’s who she’ll always be to us.