Here's how the theme is explored:
* Greg's struggle with being the "third wheel": The title itself highlights Greg's predicament of being the odd one out in social situations. He's often left feeling awkward and excluded when his friends, Rowley and his crush, Holly Hills, spend time together.
* The evolving dynamics of friendship: The story explores the changing nature of friendships as Greg and Rowley navigate their growing interests and personalities. Greg's jealousy and insecurity threaten their friendship.
* The pressure of fitting in: Greg's constant attempts to impress others and fit in with the popular crowd reveal the pressure of social conformity in middle school. His anxieties about being judged and excluded drive his actions.
* Learning to embrace individuality: Through his experiences, Greg learns the importance of accepting himself and not trying to be someone he's not. He discovers that true friendships value authenticity and mutual support.
Overall, the theme of Diary of a Wimpy Kid: Third Wheel encourages readers to understand the awkward and often confusing social dynamics of adolescence while emphasizing the importance of genuine connections and self-acceptance.