How Old Missy Is In Young Sheldon & The Big Bang Theory

3 hours ago 9

Still of Raegan Revord as Missy Cooper in Young Sheldon.

Updated Oct 22, 2026, 7:30 PM EDT

Cher Thompson is a Senior Staff Writer at Screen Rant, where she covers everything from explosive reality TV moments to cast interviews about the twists and turns of scripted dramas. With a background in creative writing, marketing, and teaching, Cher knows how to spot both the storytelling genius and the guilty pleasures in pop culture. Her work blends wit with insight, making readers feel like they’re chatting with a friend who just happens to know way too much about TV.

The Big Bang Theory's spin-off, Young Sheldon, focused not just on Sheldon Cooper, but on the whole Cooper family, paying special attention to Sheldon’s sister, Missy, who viewers knew of from The Big Bang Theory. While CBS’ original series only provided occasional appearances for Missy (Courtney Henggeler), Young Sheldon featured Missy (Raegan Revord) among its central characters. Not only did Missy’s choices impact her whole family, but the relationship she shares with her twin brother Sheldon (Iain Armitage) clearly influences him, negatively affecting him when Missy wants to annoy him and positively doing so when Sheldon needs her support.

In The Big Bang Theory, Missy is not a fully-fleshed-out character and her story is often neglected by the original show in favor of focusing on how she affects Sheldon. Young Sheldon, on the other hand, gave viewers the chance to fully understand the role that Missy played in the Cooper family, how she impacted Sheldon's youth, and (importantly) who she is as a character. By also focusing on Missy, Young Sheldon managed to make Missy more than just Sheldon’s twin sister as it details her coming-of-age story and her struggles growing up. Here’s Missy’s age in Young Sheldon and The Big Bang Theory, as well as on Georgie & Mandy's First Marriage.

How Old Missy Is In Young Sheldon

Raegan Revord as Missy Cooper in Young Sheldon

Young Sheldon starts in 1989, as stated by Sheldon himself in the prequel’s first episode. As Missy and Sheldon are twins, they are the same age, even though at the beginning of Young Sheldon Sheldon is in ninth grade with his older brother Georgie (Montana Jordan), who is 14 years old. This makes Missy 9 years old at the start of Young Sheldon, just like Sheldon. However, as the prequel series goes on, years go by and Missy is turning 12 by the time Young Sheldon season 5 ends and the series leaves off with her finally in high school.

How Old Missy Is In The Big Bang Theory

Courtney Henggeler is Missy Cooper talking with Sheldon in The Big Bang Theory

As The Big Bang Theory is set in the years the show was actually released in, Sheldon Cooper is 27 years old at the start of the show, based on Sheldon’s date of birth in 1980. Despite not appearing a lot throughout The Big Bang Theory, Missy shares Sheldon’s age, being 27-year-old in her first appearance in The Big Bang Theory season 1 episode 15.

Missy’s last appearance at Amy and Sheldon’s wedding in The Big Bang Theory season 11 episode 24 shows her at last as a 39-year-old, although her age is never really the focus of The Big Bang Theory. Instead, the majority of her appearance on the CBS hit focuses on the differences between herself and her brother. The show often focuses on her beauty and emotional intelligence compared to his genius and social ineptitude.

How Missy Changes From Young Sheldon To Big Bang Theory

Raegan Revord as Missy in Young Sheldon and Courtney Henggeler is Missy Cooper in The Big Bang Theory

Considering the little The Big Bang Theory offered about Missy, Young Sheldon did a fine job expanding the character. In Young Sheldon season 1, Missy is presented as Sheldon’s opposite, serving as a snarky rule-breaker while Sheldon fully adheres to the rules. However, when the Cooper family is in distress, Missy becomes more amicable, fully supporting Sheldon, Georgie, Mary, George Sr., or whoever may need her help. By contrast, The Big Bang Theory’s Missy is quite different.

Even if she’s just as emotionally and socially intelligent as Young Sheldon’s Missy, her life seems to have taken a sharp turn, as The Big Bang Theory season 11 episode 24 shows Missy pregnant, separated, and not exactly happy about the life she leads. However, Young Sheldon’s adult Sheldon voice-overs thankfully clarify her future after her The Big Bang Theory appearance, confirming that Missy is happier and content with her life in the future. While both shows have come to a close, Missy's influence can still be felt on Georgie & Mandy's First Marriage.

How Old Missy Is In Georgie & Mandy's First Marriage

Raegan Revord's Missy on the phone in the principal's office from Georgie & Mandy's First Marriage season 1 episode 2

Although her appearances haven't been frequent, Missy has been a part of the most recent The Big Bang Theory spinoff, Georgie & Mandy's First Marriage. Following Missy and Sheldon's older brother, Georgie (Montana Jordan), as he navigates the next chapter of his life with his wife Mandy McAllister (Emily Osment) and their daughter CeeCee, the show is far more focused around its central family than Georgie's siblings. However, Missy has appeared in a handful of episodes as the series has continued, coming in consistently to stir up trouble. In her teens, Missy is around 14 or 15 years old at the start of Georgie & Mandy.

As the series continues, Missy is continuing to grow up, and though viewers got the chance to see her as a teen on Young Sheldon, seeing Missy's teenage years play out on the spinoff series is always exciting.