Why The Big Bang Theory Replaced Its Original Female Lead With Kaley Cuoco's Penny

With every successful, long-running sitcom, there's usually at least one person left behind in the early stages who could've had a massive career-defining role but lost it for one reason or another. "Always Sunny," for instance, almost had Jordan Reid playing Dee, but she ended up departing from the series due to some messy real-life relationship drama with Rob McElhenney. It's fascinating in part because of what it tells us about the version of the show we almost had, but also because it's hard not to feel bad for Reid, who missed out on a widely beloved (and very lucrative) part, one that easily surpasses every one she had before or after.

Even with regular casting situations, it's easy to sympathize with all the people who missed out on a life-changing role. What happened to the kid who was second-up to Daniel Radcliffe for "Harry Potter," or the kids who just barely missed the cut for "Stranger Things"? It's gotta be even harder for the people who made it all the way to the filming stage, as was the case with Amanda Walsh in "The Big Bang Theory."

It turns out that before "The Big Bang Theory" was a show about a group of nerdy guys and their friendly female neighbor Penny, played by Kaley Cuoco, the show was about a group of nerdy guys and their mean new neighbor Katie (Walsh). Kate was far less charmed by their geeky behavior and far more willing to take advantage of their maidenless ways. As the show's co-creators, Bill Prady and Chuck Lorre, explained in a 2022 Entertainment Weekly interview, this dynamic played poorly with test audiences, and Walsh had to leave the show because of it.

"In the first pilot, the female character (who, at that point, was named Katie) is kind of rough. She's dangerous in a way and wasn't very nice to the guys," Bill Prady explained. He recalled hearing the first test screening reactions, saying, "They hated her, but what was amazing was that they were defending Leonard and Sheldon so much." Chuck Lorre confirmed Prady's recollection, and added:

"Yeah, we didn't realize early on that the audience viewed them as children. They were very naive and childlike, regardless of how intelligent they were. They were very vulnerable, and the audience didn't want a toxic presence around them. That's why we rewrote Katie to become Penny and made her much more charmed by the guys and kind to them, as opposed to a woman who would take advantage of them."

Although they're both happy with how the change turned out, they both seem to feel bad over how Walsh had to leave. "She was terrific in the role, but the role was misconceived," Lorre said. Prady concurred: "She was actually a very sweet person, and it was a lot of work for her to become that rough character. Afterward, she wanted to come back in for the new version of Penny, but she had been so identified as that first character that it wasn't able to happen."

Although the showrunners believed that the problem with Katie was purely a writing problem, not an acting one, CBS nevertheless asked them to hire a different actor. The result is that we got to enjoy 12 seasons of Cuoco's Penny, a charmingly sympathetic character who helps bring the gang out of their insular lifestyles while also learning to appreciate the nuances of geek culture herself.

The good news for Walsh is that, unlike Jordan Reid (who never quite got a big hit after leaving "Always Sunny"), Walsh seems to have done perfectly well for herself. She's starred in projects like "Disturbia," "Lost Girl," "Dirk Gently's Holistic Detective Agency," and was a writer on two seasons of the hit sitcom "Schitt's Creek." She's also spoken a bit about her experience with "The Big Bang Theory," and has made it clear that although the news of her replacement definitely stung, it wasn't the end of the world for her. As she explained to the author of "The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series," there were no hard feelings between her and the show's creator:

"Bill was as nice as possible about the whole thing. And then I was really fortunate that a year later, [director James] Burrows hired me for another pilot called 'The Mastersons of Manhattan with Molly Shannon and Natasha Richardson.' For me, that really validated the notion of 'It's not you,' because as an actor, you always question that. So, to get rehired by the same people for another big project was very, very validating."