Bethany Breen is the lab partner of Greg. While they're dissecting frogs, Greg feels disgusted and does not help her, as well as staying a safe distance from the dissection. Greg also once considered asking her to got to the school dance with him, but remembered the frog thing and decided against it. In Greg's Relationship Chart, she is liked by an unnamed male. She only appeared in The Third Wheel.
- Diary of a Wimpy Kid: The Third Wheel (First and only appearance)