Fake Greg Heffley is a character who pretends to be Greg when his pre-algebra class has a substitute teacher. Greg and his classmates switch seats to fool the substitute. However, the person who Greg switches seats with misbehaves. When the real teacher gets back, the substitute give her a write-up for the Fake Greg Heffley on the real Greg, which landed Greg in detention for two weeks.
- Diary of a Wimpy Kid: The Meltdown (First and only appearance)