The recent change in George's (Lance Barber) arc on Young Sheldon ruins its The Big Bang Theory crossover. While both shows exist in the same reality, they largely remained separate until the original show was announced to be ending after 12 seasons. Consequently, CBS staged a one-time crossover between Young Sheldon and The Big Bang Theory. Despite the show taking place in different time settings, it turned out to be emotionally satisfying, but the recent turn of events in the prequel show is effectively ruining it.
Debuting in 2017, Young Sheldon aired back-to-back with The Big Bang Theory for two years. This allowed CBS to establish the spinoff show in an effort to ensure that they're able to continue capitalizing on the popularity of the nerd-centric series long after it ended. That worked out fine for the network as Young Sheldon has continued to be its number one comedy. But before The Big Bang Theory wrapped up in 2019, CBS made one last attempt to solidify the series' ties to each other with a creative crossover episode.
In The Big Bang Theory season 12, episode 10 titled "The VCR Illumination," Sheldon (Jim Parsons) was all discouraged after his Nobel Prize campaign faced a major hurdle. Luckily, Amy (Mayim Bialik) unearthed an old tape of his dad delivering an empathic speech to his Medford High School football players. George's words resonated with Sheldon that they lifted his spirits up and motivated him to continue working on his Super Asymmetry paper. This established the Cooper patriarch's ability to encourage and fire up people — traits that are very important to be an effective coach. However, Young Sheldon could be debunking this since George is currently on the cusp of losing his job as Medford High School's head football coach. As George's characterization remains to be the biggest inconsistency between the sitcoms, a plot point that highlights this discrepancy could pose a major problem for the connection between the two series.
With George's career hanging in the balance, Sheldon's dad is under a lot of stress on Young Sheldon. It's difficult to gauge what's going to happen to this particular plotline on the show. Unfortunately, adult Sheldon never directly referenced this crisis on The Big Bang Theory, although he mentioned one time when his dad had to work as a cashier and it was when he was busted for stealing money. Depending on how CBS wants to move forward with his particular plotline, it could be used as the catalyst to transform him into the bad dad that he was originally described on The Big Bang Theory.
At this point, it's difficult to say what CBS is planning with regard to George's arc in Young Sheldon season 5. The character's storyline has been tumultuous thus far, especially considering his growing attraction with Brenda (Melissa Peterman) while Mary (Zoe Perry) grows close with Youth Pastor Rob (Dan Byrd). However they decide to move forward with the Cooper patriarch's current storyline, it's still imperative that it ultimately tackles his infidelity as Sheldon revealed on The Big Bang Theory.
Young Sheldon airs every Thursday on CBS.