Young Sheldon season 5 continues to have a Sheldon and Billy plot hole with The Big Bang Theory, but the spin-off prequel can use George (Lance Barber) to solve this. Adult Sheldon (Jim Parsons) often reminisced about his childhood in Texas in the original show, and he used to share fun stories from that time in his life with his Pasadena friends. This is why long before its spinoff was green-lit, fans were already familiar with some of the characters in Young Sheldon. That includes Billy Sparks (Wyatt McClure), the boy who lives next door.
When Young Sheldon premiered in 2017, CBS took the opportunity to introduce the character. He's actually one of only two characters mentioned that didn't have an older counterpart in The Big Bang Theory—the other being George.Despite this, Sheldon mentioned Billy a few times throughout the nerd-centric sitcom's run, and the prequel is taking the opportunity to finally visualize some of those stories. So far, Young Sheldon has sporadically used the Coopers' neighbor, and it's clear that Sheldon's initial description of him in the original sitcom doesn't quite line up with Billy's character in the offshoot.
In The Big Bang Theory, Sheldon describes Billy as one of his childhood bullies, earning him a spot on the socially-inept genius' all-time enemies list. But this hasn't been the case in Young Sheldon—at least thus far. Instead, Billy is depicted as more of a nuisance than a menace. He's slow, and that makes him a social outcast, but he isn't mean. In fact, Young Sheldon even double downs on this plot hole when Brenda Sparks (Melissa Peterman) admits that her son may not be smart, but he's the sweetest boy she knows. The prequel show can solve this inconsistency by using George's respective relationships with Billy and Sheldon. As the Cooper patriarch grows close with Brenda, he is also unconsciously becoming Billy's new father figure after Herschel (Billy Gardell) left. Since Sheldon can be downright mean to his dad, Billy could start being unpleasant to him in response to this perceived disrespect/under-appreciation for George.
Admittedly, Missy (Raegan Revord) has become the difficult child in the Cooper household recently. She has butt heads with both Mary (Zoe Perry) and George in Young Sheldon season 5, although it's much more heartbreaking seeing her drifting away from her dad considering their close relationship. However, Billy might not have the confidence to bully her the same way he would Sheldon for disrespecting George. For starters, Billy actually likes Missy; he was quite heartbroken when she rejected him, so chances are that he would want to limit his interactions with her. He might not even know that Missy and George's relationship is currently in a precarious position.
Secondly, Sheldon is a far easier bullying target. Missy has the social skills to retaliate, and Sheldon doesn't. Meanwhile, Georgie (Montana Jordan) is far too old for Billy to intimidate. This would be an easy way to fix Young Sheldon's Billy Sparks plot hole in relation to The Big Bang Theory. If the prequel is planning on moving forward with George and Brenda's budding affair, then it means that the Herschel kid could be spending more time with Sheldon's dad in the foreseeable future. This actually checks out with McClure being promoted to a series regular in season 5.
