5 Young Sheldon Actors Who Played Different Characters On The Big Bang Theory

After 12 seasons, "The Big Bang Theory" bid fans farewell in 2019, but thankfully, "Young Sheldon" was more than capable of filling the void that the sitcom left. The spin-off series continues telling the story of Sheldon Cooper but focuses on the early years of his life with his family in Texas. Iain Armitage fronts the show as the titular young scientist while "Big Bang Theory" star Jim Parsons provides continuity between the two series with voiceovers. In keeping with its predecessor, "Young Sheldon" welcomes a number of impressive guest stars over its seven seasons, with the likes of Ming-Na Wen, Ray Liotta, and Elon Musk gracing the small screen. But they are hardly the only notable faces to appear on "Young Sheldon" as several "Big Bang Theory" actors have also appeared on the prequel sitcom.

Chuck Lorre, who co-created "The Big Bang Theory" and "Young Sheldon," is well known for working with the same actors on multiple projects. For example, Jamie Pressly starred on two of Lorre's popular sitcoms, "Two and a Half Men" and "Mom," while Brooke D'Orsay, who appeared as two separate characters on "Two and a Half Men," plays Penny's (Kaley Cuoco) friend Christy on "The Big Bang Theory." Of course, the difference here is that "The Big Bang Theory" and "Young Sheldon" are set within the same universe, albeit in different time periods. However, even with that caveat, Lorre and co-creator Steven Molaro seem to have no qualms about bringing actors back to appear on the prequel, and it is often done in fun ways. So let's take a closer look at five of the actors who starred on both shows.

"The Kominsky Method" star Melissa Tang may not have had huge roles in either "The Big Bang Theory" or "Young Sheldon," but her appearances certainly weren't insignificant. She first shows up in "The Big Bang Theory" universe in the second episode of Season 9 as a former love interest of Leonard's (Johnny Galecki) who has just returned to work at Caltech. Her return becomes a sticking point for newlyweds Leonard and Penny, but Penny's jealousy is apparently unwarranted as Tang's character, Mandy Chow, has forgotten any and all details of her brief romantic escapade with Leonard years earlier. After briefly derailing the couple, Mandy's return actually helps bring Leonard and Penny together as they realize that always choosing to be together, even in the face of temptation, is the most important thing.

Tang is one of the first actors to guest star in both shows, making her first of two "Young Sheldon" appearances in the sitcom's pilot episode. And like on "The Big Bang Theory," her character, now Ms. Fenley, a music teacher at Medford High, is part of a larger commentary on one of the central characters. This time round, she interacts with Sheldon. Feeling a bit on the outs as an 11-year-old in high school, Sheldon finds a brief moment of comfort in the music room and impresses Ms. Fenley with his piano skills. This interaction helps establish Sheldon's genius at the beginning of the series; it shows that he has options for different career avenues he could pursue, but he's already dedicated to science.

Octavia Spencer makes a very memorable and entertaining appearance in the second season of "The Big Bang Theory." The "Hidden Figures" star shows up in Episode 5 behind the counter at the DMV where she has a trying conversation with Sheldon. With none of his friends willing to give him lifts to work, Sheldon applies for his learner's permit. Of course, Sheldon has questions, and he directs them to Spencer's character, who ultimately approves his application just to get him to shut up. Although that's the end of Spencer's role on the show, her appearance contributes to an interesting storyline where viewers get to see a different side to Sheldon. As a know-it-all genius who is typically always right, it's perhaps shocking to learn that there is something Sheldon can't do, but driving is not a skill that he acquires in this episode.

Spencer's role as an authority figure on "The Big Bang Theory" was obviously not forgotten by the showrunners either, because she was brought back to play another serious official in Season 7 of "Young Sheldon." This time, Spencer has the job of keeping Connie Tucker (Annie Potts) on the straight and narrow as her probation officer, Rhonda Thomason. Although it was another small role in "The Big Bang Theory" universe, it was a very exciting opportunity for Spencer, who is a huge "Young Sheldon" fan. She especially relished working with Lance Barber, who told TV Insider, "We finished shooting our scene, I had got out my phone, and I was sheepishly going to ask her to get a picture with her, and she beat me to it ... How cool is that?"

Penny undoubtedly has the most love interests on "The Big Bang Theory," with some of the most notable being Kurt (Brian Patrick Wade), Zack (Brian Thomas Smith), and her eventual husband, Leonard. Deserving of an honorable mention, though, is Michael Trucco's Dr. David "Dave" Underhill. He appears in Season 2, Episode 11, and is accidentally introduced to Penny by Leonard as he and Dave are working on a project at Caltech together. It seems like Dave may be the one to break Penny's bad dating streak, as he seems like the perfect guy, but it's not long before she discovers he's been lying to her and is actually married.

Penny learns the hard way that she's more attracted to the idea of Dave, just like Mary (Zoe Perry) on "Young Sheldon," who becomes attracted to the idea of Rusty (Michael Trucco), a fictional character she creates. In Season 6, Episode 3, Mary uses romance novels to fill some of her time as she's still estranged from her church. However, she believes she can do a better job of writing one and puts her pen to paper. She quickly creates Rusty and her alter-ego Marie, but like Penny, Mary learns the lesson that fantasy can be overrated. On the other hand, her writing ignites a spark of passion back into her relationship with George. Ultimately, Trucco's role on "Young Sheldon" ended up being a fun way for the series to tie itself to its predecessor, as well as highlight some of the unexpected similarities between Mary and Penny.

Jason Kravits is another actor to appear in both "The Big Bang Theory" and "Young Sheldon," but unlike the other names on this list, he guest-starred on the prequel series before securing a role on the original sitcom. In Season 1, Episode 6 of "Young Sheldon," Kravits appears as NASA administrator Dr. Hodges, who gives a talk to Sheldon and Georgie's (Montana Jordan) high school class. Taking every opportunity to prove he's the smartest person in the room, Sheldon proposes a way for NASA to fly reusable Booster rockets and save a lot of taxpayer money. When Dr. Hodges dismisses him, Sheldon makes it his mission to prove him wrong and discovers his passion for theoretical physics at the same time — and as "The Big Bang Theory" fans know, this becomes his future career.

After "Young Sheldon," Kravitz returned to "The Big Bang Theory" universe years later but played a completely different character. He obviously impressed the showrunners enough as Dr. Hodges that he was brought back to cause tension between Penny and Bernadette (Melissa Rauch) in Season 12, Episode 17. He plays a pharmaceutical rep named Danny Jacobs, a rival of Bernadette's who tries to poach Penny to work for him while they're at a conference in San Diego. However, although she's intrigued by his lucrative offer, Penny ultimately turns him down.

Both of Kravits' appearances in "The Big Bang Theory" universe are not without consequence. Penny and Bernadette's friendship became stronger for being tested, and Sheldon may never have had the career he did that led to his Nobel Prize.

While all the other actors on this list simply enjoyed guest appearances on both "The Big Bang Theory" and "Young Sheldon," Lance Barber advanced to a series regular on the spin-off, taking on the important role of Sheldon's father, George Cooper. Of course, he first appears in this TV universe in Season 5, Episode 11 of "The Big Bang Theory" as Leonard's high school bully Jimmy Speckerman. The gang runs into Jimmy by chance in a bar, where Leonard is shocked to be greeted by him like an old friend. Still holding onto a lot of anger about the past, Leonard agrees to meet Jimmy for a drink so he can finally stand up for himself. This leads to a fake, alcohol-induced apology on Jimmy's part that is promptly forgotten the morning after.

Interestingly, this character is much more akin to Sheldon's description of George Cooper Sr. on "The Big Bang Theory" than the one viewers see on "Young Sheldon" because Barber had the opportunity to really humanize the character. The character of Jimmy was a great stepping stone for Barber, though, who credits the role with helping him land the part of George. "Bless him, [Chuck Lorre] uses people that he likes. ... To be in his family of shows is a pretty privileged position," Barber noted during an interview with Harper Creek High School's HCTV.

For Barber, playing George became the role of a lifetime, and he especially enjoyed the challenge of giving him real depth rather than simply being the punchline to jokes as he was on "The Big Bang Theory." As the heartfelt tributes for Iain Armitage and Jim Parsons' characters in the "Young Sheldon" funeral episode show, Barber's version of George really had a profound effect on Sheldon's character.