Young Sheldon Had a Secret Big Bang Theory Cameo From Kaley Cuoco

It's been nearly a year since The Big Bang Theory came to a close, wrapping up the stories of Sheldon, Penny, Leonard, and more. The show's spinoff, a Young Sheldon prequel series, has continued on the franchise's geeky spirit, while also providing some weird connections to the flagship series. An episode from Young Sheldon's current season was no exception, as it has been confirmed that a December episode of the series had an uncredited cameo from one of The Big Bang Theory's stars. TVLine recently confirmed that Kaley Cuoco, who played Penny on TBBT, lent her voice to Young Sheldon's "Teenager Soup and a Little Ball of Fib" late last year.

The episode sees young Sheldon (Ian Armitage) panicking about an upcoming swim test at school, as he grows anxious about the bacteria that is in the pool. In one scene, Sheldon literally talks to the pool -- and Cuoco provided the voice of the pool, as it speaks back.

"That was absolutely the voice of Kaley as pool water," series co-creator Steve Molaro explained. "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.'"

"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?'" Molaro recalled. "She just laughed and said, 'Absolutely, I do.'"

Once Cuoco signed on for the job, the question remained how much the series wanted to hype up its potential "crossover" -- if at all.

"Sometimes I feel a little weird about things being over-promoted," Molaro said, "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."

This is just the latest connection that Young Sheldon has had to TBBT, after younger versions of the adult characters appeared in a montage during the show's season finale.

"The goal in seeing the Big Bang characters as kids was to pay tribute to the Bang series finale, which also aired that night," Molaro said of a potential return of the younger characters at the time. "So, it's unlikely. But I'll never say never."

Did you catch Kaley Cuoco's cameo on Young Sheldon? Share your thoughts with us in the comments below!