The main comedic thread involves Sheldon hiring Stuart to be his social surrogate.
In The Big Bang Theory explores themes of social surrogacy and family friction as the characters prepare for the season's final narrative arc. The episode, which aired on May 5, 2016, is primarily split between Sheldon’s ethical dilemmas at a movie line and Penny’s desperate attempts to bond with her mother-in-law, Dr. Beverly Hofstadter. The "Swapsies" vs. "Cutsies" Dilemma [S9E23] The Line Substitution Solution
Penny spends the day trying to win Beverly’s approval, but she feels insulted when Beverly focuses more on the scientific achievements of Amy and Bernadette. The main comedic thread involves Sheldon hiring Stuart
Summary. Sheldon hires Stuart to spend the day with Amy when he'd rather go to a movie screening. Also, Leonard's mother, Beverly, The Big Bang Theory Wiki | Fandom "The Big Bang Theory" The Line Substitution Solution - IMDb Beverly Hofstadter