For twelve seasons, The Big Bang Theory delighted fans with its nerdy humor, quirky characters and long-running recurring bits. However, one mystery remained up until the very end: Penny’s last name. As the only female member of the original cast, Kaley Cuoco’s character appeared in every episode, but her last name was left shrouded in mystery until one Reddit user pointed out that the series slyly revealed it in Season 2.
Fans came up with all kinds of wild theories over the years to explain Penny’s lack of a last name: Penny was a spy, Penny was her stage name, she’s following in the footsteps of Madonna and Cher and simply doesn’t have one. The truth is much simpler. The original pilot did not feature Penny, but rather a street smart retail store clerk named Katie, played by Amanda Walsh. Katie didn’t perform well with test audiences, so she was replaced with Penny, whose bubbly, naive personality better balanced Sheldon (Jim Parsons) and Leonard (Johnny Galecki). Her lack of a surname was nothing more than an oversight. By the time it became a fan-favorite mystery, there was no natural way to reveal it.
Superstition also played a role in maintaining the mystery. At a 2019 WonderCon panel prior to the series finale, executive producer Steve Molaro was asked if Penny’s last name would be revealed. He made it clear it’s one mystery that the writers intended to leave unresolved, adding, “[Eventually] we got nervous and superstitious about giving her one.” Cuoco expressed a similar sentiment to CBS News in 2017. Though she had “an idea” of what Penny’s last name could be, Cuoco was as in the dark as the fans about her character’s full name and preferred it that way, saying, “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.”
Fan wondered for years what Penny’s last name was, given that every other major character on The Big Bang Theory had their full names used frequently. However, as Reddit user points out, it seems Penny’s last name was actually revealed in Season 2, so subtly that most viewers never noticed. In Season 2, Episode 18, “The Work Song Nanocluster,” Penny enlists the help of the boys in starting a business making and selling flower barrettes called “Penny Blossoms.” Sheldon delivers her a package of materials with the name “Penny Teller” on the label.
Before settling on the sitcom’s rightful name, the Chuck Lorre and Bill Prady comedy was going to be called “Lenny, Penny, and Kenny.” Thankfully, the audience escaped the forced rhyme scheme (and calling Galecki’s character “Lenny”). The creators changed Kenny to Sheldon to honor Sheldon Leonard, one of the most notable TV producers in Hollywood history. The significance of Penny’s name remains unknown but could pay homage to the magical comedy duo Penn & Teller. Teller even appeared in an episode of the final season as Amy Farrah Fowler’s father.
It’s unclear if the show’s creators intended to reveal the name or even remember the mysterious package because over the years people involved in the show repeatedly claimed that Penny’s last name was either a secret or had never been written. As such, the lore surrounding Penny’s surname will likely continue, though once she and Leonard were married she became Penny Hofstadter. Still, the quickly glimpsed mailing label seems like the most definitive answer that The Big Bang Theory fans will be getting for one of the show’s biggest unresolved questions.