Here's what Young Sheldon season 4's The Big Bang Theory surprise cameo appearance by Amy means. While both shows exist in the same universe, their details don't already line up. But occasionally, CBS likes highlighting their connection as it was in the Young Sheldon season 4, episode 1 titled "Graduation."
Originally planned to be the season 3 finale of Young Sheldon, this outing had to be rearranged due to the coronavirus pandemic that cut their last year short to only 21 episodes instead of the usual 22. It turns out, however, that the outing was worth the wait, especially toward the end, as the voiceover provided by Sheldon from the distant future reveals the name of his son, Leonard Cooper. During the narration, he also shared that he wanted his name to be Leonard Nimoy Cooper, but Amy wouldn't let him. That's when The Big Bang Theory's Amy also joined in, telling him that he's lucky she agreed to the name Leonard in the first place.
It was a great Easter egg for The Big Bang Theory fans after the show ended its 12-year-run on CBS last year. Loyal viewers of the original series, admittedly, aren't exactly fond of it because of Young Sheldon's lax approach to continuity. The prequel tends to contradict what's been established in The Big Bang Theory to service their narrative and that understandably doesn't sit well with some. But, with the long-running sitcom now officially wrapped up, Young Sheldon is being more proactive in appealing to its parent show's massive community and one way of doing that is regularly bringing in characters of The Big Bang Theory for a brief but meaningful cameo.
The confirmation that Sheldon and Amy have a son in the far future doesn't only reveal his name, but also his potential intellectual capabilities. As the son of two geniuses, not to mention the winners of the Nobel Prize in Physics, there's a high expectation that he, too, will be smart. Initially in their relationship, this was an important motivation for both parties to continue hanging out with each other, with Sheldon only wanting to procreate in a Petri dish. While he eventually wanted to do things naturally as their romance progressed, he was still focused on the idea of having clever kids.
While Young Sheldon didn't explicitly confirm or deny the possibility that their son is also intellectually gifted, creator Steve Molaro recently shared that the voiceover is happening around 10 to 11 years into the future of The Big Bang Theory. And if Leonard Cooper has already had a good graduation party like his, it means that he may have also finished high school at a very young age. Even if the boy only finished grade school like Missy did in the Young Sheldon season 4 premiere, he will still be a couple of years ahead of the typical schooling schedule. Assuming that Amy got pregnant immediately after The Big Bang Theory ended, he would only just be 9 or 10 years old when he graduates from grade school, which is still younger than Missy who's 11 years old.
The Big Bang Theory may have already wrapped up, but CBS has the opportunity to continue its story, albeit in an indirect way, through Young Sheldon. Since the events of the prequel series are told from the perspective of adult Sheldon, they can reveal more information about the future looks like for him and the Pasadena gang via references like this one. They don't even need cameos to effectively do this as Sheldon can just casually relate his experiences from childhood to the ones he's having later in his life.