The Big Bang Theory originally had a very different version of Penny — but fortunately the showrunners decided to make some changes. Kaley Cuoco played the only main female character in the series in its first three years, acting alongside Jim Parsons (Sheldon), Johnny Galecki (Leonard), Simon Helberg (Howard), and Kunal Nayyar (Raj). It wasn't until season 4 before the show brought in Melissa Rauch's Bernadette and Mayim Bialik's Amy, which not only expanded The Big Bang Theory's cast, but also increased the female representation in the sitcom. As the main female lead of the show, Penny appears early in The Big Bang Theory's premiere episode back in 2007. From then on, Penny became a constant figure in Apartment 4A — especially after she met Howard and Raj.
Prior to The Big Bang Theory's official premiere, its unaired pilot had a significantly different cast of characters aside from Leonard and Sheldon. Penny and the other two boys weren't written, and in their place were two other female characters. Gilda, played by Iris Bahr, is reminiscent of Sara Gilbert's Leslie Winkle, and Katie, portrayed by Amanda Walsh, is arguably the original incarnation of what would be Cuoco's character. She's street-smart, confident, sexy, and has no enthusiasm whatsoever for the boys' intelligence or interests, which were some of the notable characteristics of Penny in the series. Creators Bill Prady and Chuck Lorre decided on scrapping Walsh's part after her character got a negative response from the audience during test screenings.
The Original "Penny" Was Too Mean
While Katie and Penny are similar, the viewers thought that the former was too harsh on the boys. And since the nerdy combo of Leonard and Sheldon quickly endeared themselves to the public, fans were immediately overprotective of them. Because of this, having someone who came across as mean-spirited as Katie interacting with them just didn't work.
The great thing about Penny and how Cuoco played the part is that, despite her usual nonchalance towards the boys' academic and nerdy interests, she wasn't mean to them. Yes, there's some ribbing on her part, but when it comes down to it, she's a dependable friend to all of them. No matter how much Sheldon annoyed her or Howard annoyingly flirted with her, she offered her help when they needed it. Though Katie only appeared in one episode, and she could have changed over the course of The Big Bang Theory had she stayed, it was a bit off-putting seeing how she treated the two male key players in the series.
It's difficult to tell if The Big Bang Theory's popularity would still have exploded like it did if CBS moved forward with the show's original pilot. However, looking back on its 12 years on the air, it's difficult to imagine any other character filling the role that Penny did as the audience surrogate for the show. Admittedly, though The Big Bang Theory had some problematic treatment of her character, especially in the very early years of the sitcom, no one can deny that Cuoco had great chemistry with Parsons and Galecki, as well as the rest of the cast.
Penny Went On To Have The Best Arc In The Show
Kaley Cuoco's career skyrocketed after playing Penny on The Big Bang Theory — and her character arguably had the best arc on the show. It's necessary for characters to change throughout an overarching narrative, and many of TBBT's cast went through steep transitions and major life events. Most of the crew got married, with Howard and Bernadette having their own children, Amy and Sheldon wed, and Penny and Leonard also got married. Howard's arc started early in the series and sort of plateaued. Sheldon himself had a good arc, and so did Leonard. However, Penny's character is night and day from the beginning of The Big Bang Theory to its finale. She started out as a flaky actress/waitress who truly showed more interest in her dating life than her ambitions. Over the course of the series, she slowly let go of her more intangible hopes and dreams to have a successful career and marriage. All in all, Penny changed the most out of everyone in the group, and it was obviously the right choice to cast her character over Katie in the pilot of The Big Bang Theory.