The Big Bang Theory Scene That Made Kaley Cuoco Break Down In Tears

For a sitcom that features a laugh track, Chuck Lorre's hit CBS show "The Big Bang Theory" features some unexpectedly emotional moments ... including one in season 6 where Penny (Kaley Cuoco) pretty casually tells her boyfriend Leonard Hofstadter (Johnny Galecki) that she loves him for the very first time. So, how did Cuoco feel while she performed that scene?

In an interview with TVLine's Matt Webb Mitovich shortly after the airing of the episode (in which Leonard feels jealous that Penny is spending a lot of time with a guy in one of her community college classes), Cuoco discussed the moment where Penny, almost as a throwaway, tells Leonard that the other guy is unimportant because he, being Leonard, is the guy she loves. "I knew that [executive producer Steven] Molaro and the writers had been toying with the idea [of Penny saying 'I love you']," Cuoco said. "Weeks later, when we saw the script and did a table read, I thought, 'Oh my God,' it was such a well-written scene. Then, on the shoot night, we actually did that in one take. Johnny and I were actually talking about it yesterday, how we literally felt like Leonard and Penny in that hallway. We didn't even think there was an audience there, that's how dead silent it was. It just was so perfect, Steve and Chuck [Lorre] came out and said, 'We're going to move on. We don't want to touch that.'"

When Mitovich pointed out that Cuoco looked genuinely teary during the scene, Cuoco confirmed that, yes, she cried for real during filming. "Completely," Cuoco said regarding her glassy, teary eyes. "I cried at the table read. I cried in the rehearsal. I cried in run-throughs. That's why I had to take such a long beat, because I thought, 'If I close my eyes, tears are just going to come streaming down my face,' and I wanted it to look more pent-up. I thought, 'Oh, they'll tighten that [in editing],' but they left it all in there. I guess they liked it."

It's particularly interesting that Penny chooses this precise moment to tell Leonard that she loves him — largely because one of their many breakups came in season 3 when Leonard said "I love you" and tried to pressure Penny into saying it back before she was ready. Meanwhile, in "The 43 Peculiarity," Penny says it matter-of-factly after Leonard complains that men are always staring at her in public. "Leonard, why do you always do this?" Penny says, sounding a little aggravated at first. "Listen to me, you are the one I'm with! You know I love you, so will you please relax because you're driving me crazy!" When they both realize what she's said — and when Leonard points out that it's the first time Penny has ever said "I love you" — they both immediately start crying, overwhelmed by the unexpected admission.

In the same TVLine interview, Cuoco added, "It made perfect sense that she would blurt them out and not even realize it. And you saw the vulnerability at the same time. I feel like Penny's got just as many issues as Leonard, in different ways, and this has obviously been very difficult for her, so I loved that it came out without her knowing. It shows that she meant it. It was really the first time I felt like I was actually in that moment, that I was talking to Leonard — as cheesy as that sounds. It's been an amazing and crazy road, almost six years up to that point, so it's just such a cool moment."

Apparently, the super-casual way Penny tells Leonard that she loves him for the first time caused some issues amongst the writers of "The Big Bang Theory." In Jessica Radloff's book "The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series," writer Tara Hernandez says she pitched the idea that Penny would basically blurt it out, but her colleagues objected to the fact that the episode didn't center around the admission. (Later on, Jim Parsons' Sheldon Cooper and Mayim Bialik's Amy Farrah Fowler got an episode in season 8, "The Prom Equivalency," that basically exists to build up to Sheldon telling Amy that he loves her.)

"[The pitch] ignited fire in the room, because the episode wasn't built around an 'I love you" the way the prom episode was built around it for Sheldon and Amy in season 8," Hernandez told Radloff. "The Leonard-Penny 'I love you' came up really organically when they were having a moment of insecurity of Penny working with this classmate who Leonard was threatened by. I just said it in the writers room, like, 'Leonard, I don't know why you're so jealous, you know I love you, so relax.'"

Unfortunately for Hernandez, she was newer to the writing team, so she got dismissed initially — until executive producer Steve Molaro stuck up for her and the idea. "It got pitched that easy, and everyone was like, 'No, no, no, she hasn't said it before! But you're newer to the room, you might not know' [...] I remember everyone really jumping down my throat about it, like, 'No, we're not there yet!' And to his credit, Steve Molaro just sat with it, and was like, 'Yeah. I think it's time. I think it's the time for I love yous.' Sheldon and Amy were much more premeditated; Leonard and Penny were not."

Hernandez and Molaro were right about this moment, especially because it was so authentic to Penny's character that Kaley Cuoco ended up crying in real life. "The Big Bang Theory," including "The 43 Peculiarity," is streaming on Max now.