Bethany Breen is a character that only appears in the book The Third Wheel. She is assigned to be Greg Heffley's lab partner. While they're dissecting frogs, Greg feels so disgusted that he refuses to help her, staying a safe distance from the experiment. Greg also once considered asking her to go to the school dance with him, but remembered the frog incident and decided against it. Her only other reference is in Greg's Relationship Chart, in which she is liked by an unnamed male.
- Diary of a Wimpy Kid: The Third Wheel (First and only appearance)