Every Big Bang Theory Character & Actor In Young Sheldon

The events of Young Sheldon may have taken place before The Big Bang Theory, but some characters and actors eventually made their way to the spin-off in varying ways. Debuting in 2017, the beginning of Young Sheldon takes place around two decades before the events of The Big Bang Theory. However, there are several Young Sheldon characters in The Big Bang Theory, and vice versa. Jim Parsons, who played adult Sheldon, provided the narration in the prequel, but he was far from the only crossover actor to appear on both shows.

When it was announced in 2018 that The Big Bang Theory was ending, CBS 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. In addition to The Big Bang Theory and Young Sheldon event, CBS linked the shows 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, and the prequel also featured the young versions of Sheldon's friends in season 2 to celebrate The Big Bang Theory finale.

Sheldon Cooper

Played By Jim Parsons In The Big Bang Theory And Iain Armitage In Young Sheldon

Credit: CBS via MovieStillsDB

Given that Sheldon Cooper is the titular character in Young Sheldon, it's little surprise that Jim Parsons appeared in some form, featuring as both the narrator and in-person in the show's final episode "Memoir". 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.

Mary Cooper

Played By Laurie Metcalf In The Big Bang Theory And Zoe Perry In Young Sheldon

Another obvious character who appeared in both Young Sheldon and The Big Bang Theory is Sheldon's mom, Mary Cooper. 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. Mary Cooper regularly appeared in The Big Bang Theory, in which she was played by Laurie Metcalf, and a main character in Young Sheldon when played by Zoe Perry.

Mary Cooper first appeared in The Big Bang Theory 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.

Missy Cooper

Played By Courtney Henggeler In The Big Bang Theory And Reagan Revord In Young Sheldon

Missy Cooper was a main character in Young Sheldon (played by Reagan Revord), but she also appeared in multiple episodes of The Big Bang Theory (played as an adult by Courtney Henggeler). 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 Reagan Revord's younger version of Missy debuted 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.

Meemaw

Played By June Squibb In The Big Bang Theory And Annie Potts In Young Sheldon

Annie Potts played Meemaw, Sheldon's grandmother, in Young Sheldon, but despite being mentioned regularly in The Big Bang Theory it wasn't until late in the original show that she was seen on-screen when played by June Squibb. 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.

Leonard Hofstadter

Played By Johnny Galecki In The Big Bang Theory And Isaac Harger In Young Sheldon

Johnny Galecki's Leonard was a main character in The Big Bang Theory, but Isaac Harger played a younger version of Sheldon's roommate in the Young Sheldon season 2 episode "A Swedish Science Thing and the Equation for Toast". 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.

Penny

Played By Kaley Cuoco In The Big Bang Theory And Quinn Aune In Young Sheldon

Just like Leonard, a child version of The Big Bang Theory mainstay Penny (Kaley Cuoco) appeared in Young Sheldon season 2, with Quinn Aune appearing as Penny at four-years-old. 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. Penny and Sheldon's friendship became an important part of the show, so it was fitting that Young Sheldon featured a four-year-old of Penny sleeping in Nebraska in the season 2 finale as an homage to The Big Bang Theory ending.

Howard Wolowitz

Played By Simon Helberg In The Big Bang Theory And Ethan Stern In Young Sheldon

Howard (Simon Helberg) and Sheldon had a somewhat tense friendship in The Big Bang Theory, but they were still close, so it was touching that Young Sheldon included younger Howard in season 2 (played by Ethan Stern). 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.

Bernadette Wolowitz

Played By Melissa Rauch In The Big Bang Theory And AJ Coggeshall In Young Sheldon

Young Sheldon also visited the future microbiologist and Howard's eventual wife, Bernadette, in her childhood home in Yorba Linda, California in the special The Big Bang Theory series finale tribute in season 2. Bernadette was a later entry to The Big Bang Theory cast, but Melissa Rauch's character became an instant fan favorite and was integral to the show, with Young Sheldon featuring AJ Coggeshall as the five-year-old version of her.

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.

Raj Koothrapalli

Played By Kunal Nayyar In The Big Bang Theory And Rishabh Prahbhat In Young Sheldon

Rounding up Sheldon's male friends on The Big Bang Theory is Raj, who specializes in astroparticle physics. Raj was played by Kunal Nayyar in The Big Bang Theory, with the child version portrayed by Rishabh Prahbhat in Young Sheldon. 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.

Amy Farrah-Fowler

Played By Mayim Bialik In The Big Bang Theory And Lily Sanfelippo In Young Sheldon

Sheldon's eventual wife Amy Farrah-Fowler not only appeared as a younger version in Young Sheldon, but Mayim Bialik reprised her The Big Bang Theory role for the prequel's finale episode, "Memoir". Like Bernadette, 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, who was seen reading Little House on the Prairie book. But aside from that, the adult Amy also 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.