Young Sheldon debuts a more fun version of Mary (Zoe Perry), but The Big Bang Theory already spoiled the ultimate fate of this new iteration of the character. After getting fired from the church in light of Georgie's (Montana Jordan) pregnancy news, Mary deals with another crisis of faith. As she figures out her relationship with her religion, she uses the time to let loose to the delight of both Meemaw (Annie Potts) and George (Lance Barber). Unfortunately, they shouldn't get their hopes up too high that Mary will maintain this persona in the long run.
As the first Cooper to appear on The Big Bang Theory, the nerd-centric sitcom has confirmed that sooner or later, Mary will stop being fun and revert to her old, buttoned-up self — if not worse. Throughout the CBS show's 12-season-run, Sheldon's mother visited Pasadena countless times, and every time she appeared, she acted like a religious zealot who was extremely judgmental, even to some of his son's own friends. She shamed Penny (Kaley Cuoco) for her having an active love life, and made racist remarks against Raj (Kunal Nayyar). Mary also bad-mouthed her own family, including Georgie and Missy. Most notably, however, she got into an intense conflict with Leonard's (Johnny Galecki) mother, Beverly (Christine Baranski) simply because she wasn't religious like her.
For now, Mary will continue to be relaxed and loose in Young Sheldon, which is a great way to further explore the character. Since it debuted in 2017, The Big Bang Theory prequel spin-off maintained its depiction of the Cooper matriarch as a devoted Christian, to the point that it has become the hallmark of the character. While the Cooper family, particularly George, evolved through their life experiences, Mary continued to be a one-dimensional character who is defined only by her relationship with her church. She had been so invested in pleasing her peers - a bad trait that Missy (Raegan Revord) got - that she tended to de-prioritize her family. Now that she is separated from the congregation, Young Sheldon is allowed to show a different side of her; maybe the family comedy can even reveal how she was before she became an overly-devout Christian.
Mary's trajectory in Young Sheldon season 6 is arguably the most interesting personal arc in the show thus far, simply because it isn't something that has been tackled before. Granted that her fun era will eventually end, going through this phase makes her history much richer. Perhaps, it could even provide additional context for her actions when she appeared on The Big Bang Theory.