In a crossover between Young Sheldon and The Big Bang Theory, George's insult towards Sheldon is proven by Penny. In Young Sheldon Season 6 Episode 4, George challenges Sheldon's teaching abilities by using reverse psychology. This isn't the first time Sheldon's teaching skills have been questioned; Penny previously declared that Sheldon sucks at teaching in The Big Bang Theory. The issue lies not in Sheldon's intelligence but in his attitude. Like his mother Mary, Sheldon tends to be egotistical and judgmental, making it difficult for him to connect with those who aren't as smart as he is. On The Big Bang Theory, Sheldon struggled to teach Penny Physics without criticizing her. However, when Howard joined his class, Sheldon unabashedly looked down on him due to his disdain for engineers. Little did Sheldon know that Howard was actually a capable student, highlighting Sheldon's shortcomings as a teacher.
Interestingly, Penny has a special connection with George despite never meeting him. She indirectly criticized George on Young Sheldon, and she shares the same criticism of Sheldon's teaching ability. Moreover, Penny knows about George's impending cheating scandal, something Sheldon opened up to her about during a heart-to-heart conversation on The Big Bang Theory. Penny's relationship with Sheldon mirrors that of George's, as she showed patience and love while still calling him out when necessary.
This crossover showcases the continuity between the two shows and highlights the similarities between George's criticism of Sheldon on Young Sheldon and Penny's criticism of Sheldon's teaching on The Big Bang Theory. It emphasizes Sheldon's character flaws and the complexities of his relationships with both his father and Penny.