Feeling no longer challenged by the curriculum at Medford High, 9-year-old Sheldon Cooper decides to audit a college course on . The class is taught by Dr. John Sturgis (played by special guest star Wallace Shawn), a professor with whom Sheldon has already established a pen-pal relationship. The episode's primary narrative threads include:

Young Sheldon: Gluons, Guacamole, And The Color Purple - IMDb