There were plans to have Mary Cooper and Beverly Hofstadter meet as early as season 6, but it didn't happen until this episode because Laurie Metcalf and Christine Baranski weren't available at the same time any sooner.
First appearance of Leonard's mother in Pasadena since season three.
Also aired on Kunal Nayyar's 34th birthday
Aired on Johnny Galecki's 40th birthday
Sheldon states everyone loves stories of Sheldon Cooper Boy Genius. Two years later, Young Sheldon (2017) premiered, which is about Sheldon as a boy.