The Bizarre Kaley Cuoco Cameo You Likely Missed In Young Sheldon

It's hard to make a successful network television show. It's even harder to make a successful spin-off of a successful series. Audiences have a certain expectation and, when it comes time to follow another character or two elsewhere, it can get tricky. But CBS hit it out of the park with "Young Sheldon," which focused on a young Sheldon Cooper as he was growing up in Texas long before the events of "The Big Bang Theory," itself one of the most successful sitcoms of the 2000s.

Because "Young Sheldon" takes place decades before the events of the show that inspired it, it was difficult to have characters from "The Big Bang Theory" show up. However, the show's producers did manage to sneak Kaley Cuoco in during the series' third season for a stealthy cameo. Cuoco, of course, played Penny on "The Big Bang Theory" for the entirety of its 12 season run, serving as an anchor of the ensemble.

When it came time to sneak her into "Young Sheldon," though, it was all about Cuoco's voice rather than actually having her appear on screen. The moment came in the episode "Teenager Soup and a Little Ball of Fib," which sees Sheldon (Iain Armitage) faking being sick to avoid taking a swimming test at school. Cuoco wound up providing the voice of the pool water. In a 2020 interview with TVLine, series co-creator Steve Molaro explained how it all came together:

"That was absolutely the voice of Kaley as pool water. I needed someone to do the voice. I knew I wanted it to be female and kinda sexy, and I said, 'Well, duh! Kaley is perfect for this.'"

So, how did Molaro sell this bizarre role to Cuoco? After all, Cuoco has stayed quite busy since "Big Bang Theory" went off the air, voicing the title character in "Harley Quinn" and "The Flight Attendant," among other projects. Even so, it was an easy yes from the actor:

"I said, 'Hey, I have a weird pitch for you: Sheldon has a nightmare, and he has to go to this pool, and he speaks to the pool water. Do you want to be the voice of pool water?' She just laughed and said, 'Absolutely, I do.'"

Even though the role was small and relatively strange, it was also an important one. Cuoco became the first former "Big Bang Theory" star to lend their talents to the spin-off after Jim Parsons, who operated as an executive producer on the series in addition to serving as the narrator. To help close out "Young Sheldon," Parsons ended up reprising his role as Sheldon in the flesh alongside Mayim Bialik's Amy in the final season. Setting that aside, though, Cuoco's voice role was a nice touch for fans.

What's interesting is that CBS didn't promote Cuoco's cameo ahead of the episode's premiere. Wouldn't the network have wanted to highlight the return of a "Big Bang Theory" star to the universe? Maybe, but as Molaro explained in the same interview, everyone involved in making the show agreed the moment was all the more impactful because it'd been kept secret:

"Sometimes I feel a little weird about things being over-promoted, and as awesome as it was, I don't know that that should be the kind of thing that appears in promos. [Kaley] wanted to hold it under wraps [as well], so that if you figured it out, that was a little Easter egg for you, so we were all on the same page about that."

The series ended up running for seven seasons in total, with "Young Sheldon" season 7 concluding things in 2024. Still, the larger "Big Bang Theory" universe lives on with yet another spin-off in the form of "Georgie & Mandy's First Marriage." Whether or not Cuoco or any of the other "Big Bang Theory" stars make appearances on that show remains to be seen.

"Young Sheldon" is streaming now on Netflix and Max, or you can grab the complete series on DVD from Amazon.