The events of Young Sheldon may have taken place before The Big Bang Theory, but some characters and actors who were first featured in the latter series eventually made their way to the spin-off in varying ways. Debuting in 2017, the CBS prequel follows its titular character in his years living in Texas with his family before eventually settling in Pasadena and meeting his loyal friends. The beginning of Young Sheldon takes place around two decades before the events of The Big Bang Theory however, some key players from the original show also appeared in the chronologically earlier project thanks to some creative maneuvers from the people behind both sitcoms.
Young Sheldon was already running for two seasons when The Big Bang Theory wrapped up its 12-year-run in 2019. Before TBBT‘s final year, however, there was barely any effort to establish a stronger narrative connection between the two series. Though Jim Parsons, who played adult Sheldon, provided the narration in the prequel, the shows mostly existed on their own. In fact, Young Sheldon was so lax in maintaining continuity and previously established details in its parent series that there have been a series of inconsistencies — something that fans of The Big Bang Theory don’t overly like. As it was announced in 2018 that The Big Bang Theory was ending despite still pulling great ratings for CBS, the network started working to bridge the gap between it and Young Sheldon, even resulting in a one-time crossover event despite them taking place in different decades.
Aside from the special The Big Bang Theory and Young Sheldon event, the latter has also brought in some characters from the former. CBS did it in various ways like making Mary and Missy Cooper main cast members and featuring Amy through a voice cameo in Young Sheldon season 4 premiere. In other instances, the people behind the show had to be more creative, like when the prequel featured the young versions of Sheldon’s friends in the season 2 finale in celebration of The Big Bang Theory finale.
Before he got his own TV series in Young Sheldon, Sheldon Cooper was first introduced in The Big Bang Theory as one of the five main characters of the series when it debuted in 2007. At that point, the long-running CBS sitcom was very much an ensemble project, with its focus mainly on the boys’ overall rapport plus Penny. But over time, it became increasingly clear that Sheldon was its true lead; many of the episodes were driven by his story, and even when he’s not the focal point, he remained a major factor in every narrative. No wonder he’s the first character from The Big Bang Theory to get his own spin-off.
Sheldon liked to talk about his time living in Texas with his family and being a mama’s boy, and his mother Mary was a constant character in his stories in The Big Bang Theory. She first appeared in season 1, episode 4 “The Luminous Fish Effect” when she visited Pasadena after Leonard sought her help about Sheldon’s work woes. Considering Young Sheldon‘s premise, Mary is more fleshed-out in the prequel; at times, it even reveals new details about the character that have never been mentioned before. Interestingly, The Big Bang Theory and Young Sheldon‘s versions of the character are noticeably different, highlighting the disconnect between the shows.
After Mary’s visit to Pasadena in The Big Bang Theory season 1, Sheldon’s fraternal twin sister Missy followed suit appearing in episode 15, “The Porkchop Indeterminacy.” Prior to her appearance, she had already been mentioned in the pilot episode, but the rest of the boys assumed that she would be as insensitive and high-brow as her brother. When she debuted as a young kid in Young Sheldon, the prequel doubled-down on the twins’ differences, making Missy more socially-engaged and emotionally-attuned than her brother. Despite their usual bickering, Sheldon and Missy maintain a good relationship in Young Sheldon, with the former even giving a special shout-out to his sister during his high school graduation.
He may have a soft spot for his mother, but Sheldon and his Meemaw have a much closer bond, though she is Mary’s mother. She was first mentioned in The Big Bang Theory season 2, episode 17 “The Terminator Decoupling,” followed by an appearance in season 9, episode 14, “The Meemaw Materialization” when she came to Pasadena to meet her grandson’s then-girlfriend, Amy. Since Sheldon’s family lives just across the street from his Meemaw, she’s a constant figure in Young Sheldon, even having her personal arc in the prequel which primarily revolves around her love life.
After The Big Bang Theory pilot episode was reshot following notes from CBS, only two characters from the original pilot were kept — Sheldon and Leonard. The sitcom’s whole premise hinged on their relationship as roommates and eventual friends as it’s Leonard who introduced the socially-inept genius to Howard and Raj. While there have been serious issues between the pair throughout The Big Bang Theory‘s run, they genuinely care for each other. As part of Young Sheldon‘s way to honor its parent series’ finale, its season 2 capper featured a young Leonard staying up late at night in his New Jersey Home.
As Sheldon’s closest female friend in The Big Bang Theory, Penny learned how to handle his tantrums and eccentricities over time. While Sheldon was particularly mean to her in the early years of The Big Bang Theory, shaming her for her romantic dalliance and looking down on her because of her academic achievements, Penny was mostly patient about her neighbor. This made Sheldon comfortable around her, so much so that he was willing to share traumatic stories of his childhood with her, including the revelation that he caught his dad cheating just a couple of years before he died. As with Leonard, Young Sheldon featured a five-year-old of Penny sleeping in Nebraska in the season 2 finale as an homage to The Big Bang Theory ending.
Sheldon liked to lord over his academic prowess even to his friends, and he particularly enjoyed doing it to Howard despite the fact Howard was the only one of his group of friends who had been to space. Sheldon isn’t impressed with Howard’s engineering degree and the fact that, aside from Penny, he’s the only one of the Pasadena gang without a doctorate. As a native Californian, Young Sheldon featured young Howard who was playing video games in the same house that he still lived in at the end of The Big Bang Theory with his wife Bernadette and their two kids.
Speaking of Bernie, Young Sheldon also visited the future microbiologist in her childhood home in Yorba Linda, California in the special The Big Bang Theory series finale tribute in season 2. Howard’s eventual wife Bernadette joined the cast of The Big Bang Theory in season 3 as a guest star, but after her chemistry with her future husband became clear, CBS brought her in as a regular cast. Initially introduced as Penny’s co-worker at The Cheesecake Factory, Bernie put herself through graduate school and eventually became a pharmaceutical company executive.
Rounding up Sheldon’s male friends on The Big Bang Theory is Raj, who specializes in astroparticle physics. As the only member of the Pasadena gang who’s not from the U.S., Young Sheldon featured his nine-year-old version in New Delhi, India at his study table. At the end of The Big Bang Theory, Raj was the only one left in the group who was still single as everyone else married each other. He was engaged to be married, but that fell through in the middle of The Big Bang Theory season 12. That said, considering the connection he made with Sheldon’s sister, Missy, it’s not outside the realm of possibility that it will eventually be revealed in Young Sheldon that the pair ultimately ended up with each other.
Like Bernie, Amy was a late addition to The Big Bang Theory. Introduced in the season 3 finale, she was brought in as a series regular the next year as Sheldon’s love interest. Throughout her time in the show, she evolved to be more socially open and less like her boyfriend thanks to Penny and Bernie. While her relationship with Sheldon had a lot of twists and turns, they end up getting married and winning a Nobel Prize in Physics together. Like the rest of The Big Bang Theory‘s main cast, Young Sheldon also featured a young Amy reading Little House on the Prairie book. But aside from that, adult Amy also recently made a voice cameo in the prequel series as Sheldon revealed in Young Sheldon season 4 premiere that they have a son named Leonard Cooper, confirming that the couple is still going strong.
In The Big Bang Theory season 6, Sheldon and Leonard discovered that both of them grew up watching Professor Proton’s show, and when they learned that the actor behind the character, Arthur Jeffries, was doing science shows, they took advantage of the opportunity. Since then, Professor Proton appeared a few more times in the CBS long-running show in various forms — at one point, even as a Force ghost type of character in Sheldon’s dreams. Young Sheldon had the chance to actually show just how much of a fan its titular character was of the TV personality. Throughout its four seasons, the character has been mentioned, as well as made a voice and physical cameo — more recently, Sheldon even started a college club for him.
Mrs. Wolowitz and Beverly Hofstadter
Howard and Leonard’s respective mothers were constants in The Big Bang Theory. Beverly did visit Pasadena a handful of times, especially after she began liking both Sheldon for his pragmatic take on things and Penny for being an independent woman. Howard’s mom, Mrs. Wolowitz, however, was never shown on screen, but her grating voice was regularly featured in The Big Bang Theory until she died in season 8. Both mothers made a voice cameo in Young Sheldon season 2 finale as they called to their sons.
Playing himself in The Big Bang Theory, Wil Wheaton appeared in a total of 17 episodes in the original show. Initially, Sheldon and Wil had a contentious relationship; Sheldon was mad because Wil skipped the 1995 Dixie Star Trek Convention, losing the opportunity to meet the Wesley Crusher actor and he carried that grudge for years. In Young Sheldon season 4, episode 11, a photo of young Wil can be seen on the teen magazine that Missy was reading.
Vernee Watson played the attendant at the sperm bank in The Big Bang Theory pilot, from there, she made three more appearances. While her name was never mentioned in the show, she’s credited as Althea Robinson. The actress was brought in on several episodes of Young Sheldon where she played a younger version of the same character. How she ended up in California from Texas is unknown, however.
But characters aren’t the only crossover connection between the two shows. They also feature a number of actors who appeared in both, even if they didn’t play the same character:
Playing George Sr., the Cooper patriarch in Young Sheldon, Lance Barber is a regular cast member in Young Sheldon. His portrayal mostly contradicts Sheldon’s stories of his dad in The Big Bang Theory, but it’s possible that the CBS spin-off is working its way into building towards the version of his character that his son remembers. But, long before he was cast as Sheldon’s dad, Barber already appeared in The Big Bang Theory back in season 5 playing a different character — Leonard’s bully in high school, Jimmy Speckerman.
The actress’ stint as Penny for 12 seasons in The Big Bang Theory made it easy for viewers to spot Kaley Cuoco’s voice cameo on Young Sheldon season 3 titled “Teenager Soup and a Little Ball of Fib.” Kaley Cuoco was uncredited for the role of the talking pool water in Sheldon’s dreams. Belatedly, series producer Steve Molaro confirmed that it was indeed Cuoco.
The actress portrayed Mandy Chow in The Big Bang Theory, and while she didn’t have that big a role in the series, she almost sabotaged Leonard and Penny’s marriage. Shortly after tying the knot, Leonard came clean about making out with Mandy during a drunken night; this understandably didn’t sit well with his new wife and the pair proceeded to argue in their first few days as a married couple. Melissa Tang was brought back in Young Sheldon playing an entirely different character in Ms. Fenley, the music teacher at Medford High School.