Sheldon's biggest storyline in Young Sheldon season 6's two-part finale involved the upcoming summer research program in Germany, but his eagerness to adapt to an entirely different environment contradicted what The Big Bang Theory season 10 set up. Throughout The Big Bang Theory's twelve seasons, Sheldon's rigidity often provided comic relief, especially when it let audiences laugh at it with the sitcom's other protagonists or because of the situations it put them in. The Big Bang Theory often highlighted how Sheldon's difficulties at adapting often caused him serious problems, but it rarely showed Sheldon approaching a possible challenge with gradual changes, and when it did, other characters suggested so.

However, the chance to attend the Heidelberg research program seemingly left Sheldon unfazed by the prospective routine changes in Young Sheldon season 6's ending. Not only did Sheldon do his best to obtain external financial support, something that clearly made him uncomfortable, but he also successfully introduced to his routine German food and mealtimes following the German time zone, a plan he devised and followed on his own. Even as Young Sheldon season 6 provided comic relief by showing the odd situations its titular character found himself in while trying to adapt, it raised the question of why would Sheldon be more adaptable as a kid than as an adult.

Sheldon Was Adaptable In Young Sheldon But Not In The Big Bang Theory

Sheldon's behavior got on other characters' nerves in Young Sheldon season 6, episode 21, "A Romantic Getaway and a Germanic Meat-Based Diet" but it also proved his willingness to adapt to lifestyle changes during his summer research program abroad. Sneaking in sauerkraut and knockwurst to Dr. Linkletter's lecture or covering his windows with tinfoil to sleep during the day may have raised eyebrows, but also showed evidence of Sheldon's commitment to cause minimal disruption to his routine when it was time to go to Germany.

Contrarily, Sheldon moving in with Amy in The Big Bang Theory's season 10 caused a commotion even if he approached it as a scientific experiment.

The Big Bang Theory season 10, episode 5, "The Hot Tub Contamination" had Sheldon quip back with "I think we should see other people" at Amy's request to share a toothbrush holder, showing his uncompromising attitude even after he independently accepted Amy's proposal. While talking with Penny eventually explained Sheldon's fears about their relationship turning sour like his parents' marriage, it wouldn't explain why he didn't come to that conclusion alone, considering that 14-year-old Sheldon already adapted to a summer program abroad on his own.

Even as Sheldon struggled with Penny and Leonard wanting to live without him in TBBT season 9, the conflict was only resolved once they proposed to move to Penny's gradually.

Young Sheldon Needs To Explain Why Sheldon Regressed In The Big Bang Theory

Sheldon's approach in The Big Bang Theory to any change, no matter how minimal, was often one of refusal. Whether it was Penny trying to make Sheldon knock for less or more than the usual three knocks, or Amy trying to get Sheldon used to unfinished things or tasks, Sheldon's reaction was always one of opposition in The Big Bang Theory. Young Sheldon already showed countless times a more emotionally intelligent Sheldon than TBBT's social-inept genius. Even if Sheldon's sudden change is ascribable to his father's death, Young Sheldon season 7 will have to explain how Sheldon regressed so much, as the difference from TBBT is just unavoidably evident.