Why Penny Was The Only Big Bang Theory Character Name-Dropped In Young Sheldon's Series Finale

In the series finale of "Young Sheldon" — the first major spin-off of "The Big Bang Theory" that wonders "what if Sheldon, but young?" — we see the on-screen return of "old Sheldon" as played by original "Big Bang Theory" star Jim Parsons. We also hear about one of Sheldon's dearest friends, Penny Hofstadter, played on Chuck Lorre's massively popular CBS sitcom "The Big Bang Theory," by Kaley Cuoco.  Specifically, we learn that Penny babysits Sheldon and Amy's kids. (We also see the return of Mayim Bialik's Amy Farrah Fowler, Sheldon's wife, in the episode.)

Executive producer Steve Holland spoke to Variety after the episode aired to discuss why they chose to mention Penny over Sheldon's other friends from "The Big Bang Theory," including Howard Wolowitz (Simon Helberg), Raj Koothrappali (Kunal Nayyar), or even Penny's husband (and Sheldon's best friend) Leonard Hofstadter, played by Johnny Galecki. "We didn't want to go with the whole cast," Holland explained. "And we also wanted to keep it on Sheldon and Amy and their kids' relationship, so it just seemed like a nice coda at the end. And the Sheldon-Penny relationship was always so strong on 'Big Bang,' it seemed like a nice way to do it."

Holland is right that the relationship between Sheldon and Penny is a total standout on "The Big Bang Theory" — in fact, it might be the best relationship on the entire series! — But he went on to say that the scene featuring an older Sheldon and Amy actually paid homage to "The Big Bang Theory" in another way ... which involved some original props.

As Steve Holland said in this interview after "Young Sheldon" wrapped up its run in 2024, he and other people on the show's creative team actually rifled through the old set of "The Big Bang Theory to create Sheldon and Amy's home ... which was particularly easy because, as we learned from Holland, the set is kept as a museum on a Warner Bros lot. "We loaded the set with little nods and Easter eggs and things from the apartment and things from 'Young Sheldon' and from 'Big Bang,'" Holland said. "We didn't want it to distract from the scene that's going on, but maybe if people go back and freeze-frame afterwards, there's a lot of little hidden things decorating that set. It was really fun and emotional, actually, to pull those things back into our world."

Okay, so which items did they decide to pull for the last-ever episode of "Young Sheldon?" Obviously, Sheldon's Nobel Prize for his work on super-asymmetry, which he won with Amy in the series finale of "The Big Bang Theory," is there, but Holland said the whole setup is much more dense than you might think at first. Holland told Variety:

"There are so many items. But for one thing, and this is Sheldon's office in his house in Pasadena, the couch [from 'Big Bang'] is there. We barely focus on it, but if you're eagle eyed, it's there in the background. The DNA molecule from their apartment is there in the corner. His Nobel prize is framed on a wall behind him. There are probably 20 or 25 little things that we pulled from either "Big Bang" or "Young Sheldon" that we placed. But hopefully, if [viewers] go back and watch it a few more times, see how much they can spot."

It's interesting, considering that the set for the "Young Sheldon" finale is jam-packed full of references to "The Big Bang Theory," that Penny specifically gets a shout-out. Holland makes a solid point, though; Penny and Sheldon's relationship is probably the one that evolves the most on the show, and it deserves to get a spotlight in the spinoff's series finale.

Throughout "The Big Bang Theory," Sheldon and Penny are basically polar opposites. Penny, a gregarious aspiring actress who moves in across the hall from Sheldon and Leonard at the beginning of the series, is bubbly, social, and not scientifically minded; Sheldon is a theoretical physicist who thinks he's smarter than every single person he's ever met. (I'm not exaggerating. Half the time he talks to Howard, he just makes fun of him for not having a PhD.) Sheldon treats Penny pretty poorly for a lot of the show's early seasons, and by that, I mean he just clearly considers her to be completely inferior to him. Penny's willingness to cut Sheldon some slack and keep trying to befriend him is what ultimately helps their relationship progress.

As time goes by, it's clear that, on some level, Penny understands Sheldon better than most people. Here's an example. In the season 9 episode "The Celebration Experimentation," Amy tries to throw a surprise party for Sheldon, but it completely freaks him out and he goes to hide in the bathroom; Penny is the only person who can get him to join the party, and it's partly because she promises to simply sit in the bathroom with him all night if that's what he wants to do. By the end of the show, Sheldon announces — at the Nobel acceptance ceremony, no less — that Penny is one of his best friends in the world, so ultimately, it does feel exactly right that Penny is babysitting for Sheldon and Amy years after the series finale takes place.

"The Big Bang Theory" and "Young Sheldon" are both available to stream on Max, and the latter is also available on Netflix.