A social group is defined as two or more people who share expectations and responsibilities and have a unifying characteristic or purpose. Common types of social groups include peer groups of the same age, cliques with shared interests, clubs dedicated to activities, households within a home, primary close relationships, and secondary impersonal interactions. The document then discusses stereotypes of nerds, goths, and popular girls and how including these contrasting subcultures and stereotypes in a film opening sequence can make it more interesting for viewers by subverting expectations.